Journal of Pediatric Health Care
Volume 24, Issue 4 , Pages 258-266, July 2010

2009 H1N1 Influenza Pandemic

  • Teri Moser Woo, PhD, RN, CPNP

      Affiliations

    • Corresponding Author InformationCorrespondence: Teri Moser Woo, PhD, RN, CPNP, 10707 SW Moapa Ave, Portland OR 97219

Article Outline

Abstract 

The 2009 H1N1 influenza pandemic took health care workers worldwide by surprise. Early in the course of the pandemic it was determined that children and pregnant women were at high risk of increased morbidity and mortality from the novel influenza virus. The Centers for Disease Control and Prevention and state and local public health officials quickly rallied to develop treatment guidelines for the new strain of influenza A, including emergency approvals for off-label use of some antiviral drugs. Prevention of the spread of influenza via vaccination and environmental controls is critical to the health of children. The 2009 H1N1 influenza virus emerged too late to be included in the 2009/2010 seasonal influenza vaccine, so production of a monovalent vaccine was set in motion. Five months from when the first cases of novel H1N1 appeared in Mexico and the United States, a vaccine was being distributed to high-risk patients. Looking ahead to the 2010/2011 influenza season, it is difficult to predict 2009 H1N1 activity. The 2010/2011 seasonal influenza vaccine will include the 2009 H1N1 strain, so it is critical to get all children vaccinated early in the flu season.

Key Words: H1N1, influenza A, pandemic

 

Section Editors

 

Teri Woo, PhD, RN, CPNP

Corresponding Editor

University of Portland, School of Nursing

Kaiser Permanente

Portland, Oregon

Elizabeth Farrington, PharmD, FCCP, BCPS, FCCM

University of North Carolina

Eshelman School of Pharmacy and North Carolina Children's Hospital

Chapel Hill, North Carolina

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Objectives 


1.Describe the evolution of influenza viruses, specifically the 2009 H1N1 influenza virus.

2.Describe treatment of children infected with 2009 H1N1 influenza.

3.Discuss strategies to prevent the spread of influenza virus.

4.Discuss the 2010/2011 seasonal influenza vaccine components.

The 2009 pandemic influenza season took most health care providers by surprise, in spite of years of warning about the possibility of pandemic flu. Novel H1N1 influenza appeared to come out of nowhere and quickly spread worldwide, thanks to modern air travel. This article will discuss the H1N1 influenza virus, its unique characteristics, its impact on the population of the United States and countries worldwide, and treatment of the virus. Prevention strategies, including vaccination, also will be discussed.

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Influenza Virus 

Two types of influenza virus cause disease in humans: influenza A and influenza B. The influenza A viruses are further classified based on their surface antigens, hemagglutinin and neuraminidase. Thus influenza A viruses are named with an “H” and an “N” component: H2N2, for example. Influenza A is known to demonstrate “genetic drift,” with the virus changing slightly from influenza season to influenza season. Influenza B viruses are from two clear genetic lineages (Yamagata and Victoria) and demonstrate less genetic drift (Fiore et al., 2009). Since the 1970s the three predominate circulating influenza strains have been influenza A (H1N1), influenza A (H3N2), and influenza B. In some seasons we have seen influenza A (H1N2), probably because of a re-assortment between the H1N1 and H2N3 viruses (Fiore et al., 2009). Patients whose bodies have developed antibodies against one type of influenza virus type or subtype have limited or no immunity to another subtype of influenza. Because of antigenetic shifts, the need exists to constantly evaluate and reassess the components of the seasonal influenza vaccine.

Patients whose bodies have developed antibodies against one type of influenza virus type or subtype have limited or no immunity to another subtype of influenza.

For many years fear of an avian or “bird” flu epidemic has existed after a highly pathogenic avian influenza A (H5N1) virus was identified in Asia. Cases were seen in Asia, Europe, and the Middle East in humans who had contact with sick or dead infected birds, with limited person-to-person transmission (Fiore et al., 2009). The avian H5N1 virus was highly pathogenic and had a high mortality rate (>60% of cases were fatal in humans). There was worldwide concern that the H5N1 virus would combine with human influenza A and create a worldwide pandemic. Public health departments from the local to the national level were urged to develop pandemic influenza plans; these plans were put in place with the H1N1 outbreak.

Another animal influenza virus is swine influenza A (H1N1), A (H1N2), and A (H3N2). Swine influenza is endemic among pigs, with 30% of the pigs in the United States testing positive for swine influenza A (H1N1) (Fiore et al., 2009). Humans who work with pigs may become infected with swine influenza A, but the actual incidence of pig-to-human transmission is unknown (Fiore et al., 2009). Human-to-human transmission has not been seen in past outbreaks of swine influenza A.

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Novel 2009 H1N1 Emerges 

In March and April 2009 a new respiratory illness emerged in Mexico and in two children in the United States. It was identified as a novel influenza A H1N1 virus, similar to swine influenza A. The influenza A (H1N1) virus was not a totally new virus, but it had hemagglutinin epitopes that few humans had antibodies to. Initially it was thought that novel H1N1 was a pig-to-human transfer of swine influenza A; however, it is actually a new virus never before seen in humans or pigs. The initial naming of the new influenza “swine flu” created confusion that the virus could be transmitted from pigs. The term used to refer to the virus evolved from “swine flu” to “novel H1N1” to “2009 H1N1” in the literature to distinguish the new virus from previous H1N1 influenza A viruses.

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Initial Spread 

As previously discussed, the early cases of 2009 H1N1 virus were identified in Mexico in March and April 2009. March and April are historically a school holiday season, with families traveling for spring break or Easter break. Within 1 week of early reports of 2009 H1N1 in Mexico and California, approximately 100 children became ill with influenza-like illness (ILI) in a New York City parochial high school (France et al., 2010). The week before the outbreak the school had been on spring break, and it is thought that the virus was brought back to New York by students who had visited Mexico on vacation (France et al., 2010). The virus quickly spread throughout the United States and by May 6, 2009, there were 1487 laboratory confirmed and/or probable cases from 43 states (Centers for Disease Control and Prevention [CDC], 2009a). The first cases were reported in Canada on April 26, and by May 6, 2009, the virus had been identified in 21 countries (CDC, 2009a). Of the patients for whom travel histories were obtained, 82% had traveled to Mexico (CDC, 2009a). On June 11, 2009, the World Health Organization (WHO) declared a worldwide pandemic (National Center for Immunization and Respiratory Diseases [NCIRD], 2009).

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Unique Characteristics 

Historically, seasonal influenza virus has caused the most severe disease in the very young and the very old (those older than 65 years). 2009 H1N1 influenza demonstrated a different pattern, in that the most hospitalizations were among those younger than 65 years (NCIRD, 2009). Initial reports indicated that 40% of patients were between the ages of 10 and 18 years, with only 5% of cases in patients older than 51 years (Dawood et al., 2009). Further examination revealed that the median age for laboratory-confirmed H1N1 infection was 12 years as of July 2009, with the majority of cases in children and young adults ages 5 years to 24 years (NCIRD, 2009). Clearly younger patients had greater prevalence than older patients who were exposed to a similar strain of influenza that circulated in the 1940s and 1950s.

Another group that quickly emerged as high risk were pregnant women. From April 15 to May 18, 34 cases of 2009 H1N1 were identified in pregnant women, with 32% (11) of the women hospitalized a much higher admission rate than the general population (Jamieson et al., 2009). In the first 2 months (April 15 to June 16) of the outbreak, six deaths among pregnant women were reported to the CDC; pneumonia and acute respiratory distress syndrome had developed in all of them (Jamieson et al., 2009). A review of 2009 influenza season intensive care unit (ICU) admissions in New York City indicated that pregnant women had a 7.2 times increased risk of hospitalization and a 4.3 times risk of ICU admission over non-pregnant women (Fine et al., 2010). Pregnant women with influenza are thought to be at increased risk of severe respiratory disease because of changes in immunologic status, decreased functional residual capacity, and increased ventilatory demand (Fine et al., 2010).

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Outcomes of 2009 Influenza Season 

The influenza season officially extends from October to October, when CDC statistics are compiled on the “flu season.” Counting of H1N1 cases began in April 2009, and the CDC stopped collecting reports of confirmed or probable cases of 2009 H1N1influenza in July 2009, with 43,771 cases reported (CDC, 2010a). These cases are thought to be a significant undercount of the actual number of cases, so the CDC developed a probabilistic multiplier model to estimate the number of cases of and hospitalizations resulting from the 2009 H1N1 influenza (Reed et al., 2009). The model was developed from a study that determined that every case of 2009 H1N1 reported to the CDC represented an estimated 79 cases and each hospitalization represented an average of 2.7 hospitalized patients (Reed et al., 2009). The CDC estimates that between 39 and 80 million cases of H1N1 occurred between April and December 12, 2009, with an estimated 246,000 H1N1-related hospitalizations (CDC, 2010b). The estimate of H1N1 influenza in children aged 0 to 17 years during April to December 2009 was a mid-range of 18 million cases, 78,000 hospitalizations, and 1180 deaths (CDC, 2010b). There were 360 confirmed cases of influenza-related pediatric death in the 2009 calendar year, compared with 90 influenza-related deaths in 2008 (CDC, 2010a). Clearly 2009 H1N1 has had a significant impact on children.

Although the CDC stopped counting cases, tracking of positive laboratory specimens continues as part of the routine tracking of influenza activity. The CDC tracks the circulating influenza strains, and in 2009 influenza A (H1), influenza A (H3), 2009 influenza A H1N1, and influenza B were the circulating strains. There were three distinct peaks in positive laboratory samples for 2009 H1N1 in 2009 reported by the CDC: the week of May 9, 2009 (N = 441 H1N1 plus 517 unsubtyped influenza A), the week of June 20, 2009 (N = 3278 influenza, 99% 2009 H1N1), and the week of October 29, 2009 (N = 8268 2009 H1N1). By fall of 2009, 99% of circulating influenza virus was 2009 H1N1 (CDC, 2009b).

The CDC also tracks visits to sentinel providers for ILI. The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) consists of 3000 health care providers in 1400 health care sites across 50 states, the District of Columbia, and the U.S. Virgin Islands (CDC, 2010c). A distinct peak was seen in influenza-like illness in the fall of 2009 (Figure), with a large peak in pediatric visits (ages 0 to 24 years) seen in mid to late October 2009 (CDC, 2010c). This CDC-confirmed peak is no surprise to any PNP practicing during the fall of 2009. As of April 1, 2010, 2009 H1N1 activity has quieted down nationwide, with the exception of Georgia, which is experiencing increased visits and hospitalizations related to 2009 H1N1.

  • View full-size image.
  • Figure. 

    Percentage of visits for influenza-like illness (ILI) reported by the U.S. Outpatient Influenza-like Surveillance Network (ILINet), Weekly National Summary, October 1, 2006-March 27, 2010.

Reprinted from the Centers for Disease Control and Prevention. This figure is available in color online at www.jpedhc.org.

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Diagnosis of H1N1 Influenza 

Clinical evaluation is critical in the diagnosis of 2009 H1N1 influenza. Most children have mild illness similar to that seen with seasonal influenza, with symptoms of fever, cough, sore throat, body aches, chills, headache, and possibly gastrointestinal symptoms. Not all children with 2009 H1N1 influenza will have fever. In spite of pandemic influenza prevalence in the community, pediatric providers need to consider the differential diagnosis of other respiratory illnesses such as respiratory syncytial virus pan influenza virus, human metapneumovirus, and rhinovirus.

Definitive diagnosis of H1N1 disease is via reverse transcriptase-polymerase chain reaction (rRT-PCR) or viral culture, both of which take hours to days for results (CDC, 2009d). Rapid influenza tests will determine if the patient has influenza A, but they cannot distinguish between 2009 H1N1, seasonal H1N1, or H3N2 influenza A (CDC, 2009e). A rapid influenza test specific for 2009 H1N1 (BinaxNOW) has been evaluated and demonstrated 45% sensitivity (accuracy of diagnosing 2009 H1N1) and 98.6% specificity (correctly excluded those without 2009 H1N1) in a sample size of 3030 pediatric specimens (Cruz, Demmler-Harrison, Caviness, Buffone, & Revell, 2010). A concern for a test with low sensitivity is that a negative rapid test does not rule out 2009 H1N1 influenza A.

The CDC issued a recommendation for treatment of pediatric patients that states that testing for 2009 H1N1 influenza A should be prioritized for patients with suspected influenza requiring hospitalization (CDC, 2009c). The recommendation further outlined that patients who are high risk or have an indication for influenza treatment should begin treatment with no delay while waiting influenza diagnostic testing (CDC, 2009c).

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Treatment of H1N1 Influenza Disease 

Treatment of 2009 H1N1 disease depends of the severity of the illness and patient risk factors for the development of serious complications. The CDC has recommended empiric antiviral treatment for three groups: patients requiring hospitalization; patients with progressive, severe, or complicated illness, regardless of previous health status; and patients with risk factors for the development of serious illness (Centers for Disease Control and Prevention, 2009, Centers for Disease Control and Prevention, 2009d). Patients at risk for the development of serious illness or death from influenza are children younger than 5 years and children with certain chronic illnesses, especially medically fragile children (Centers for Disease Control and Prevention, 2009d, American Academy of Pediatrics Work Group, 2009). Box 1 lists children at highest risk of having serious outcomes of 2009 H1N1 influenza. Children who are at low risk with mild disease can be treated for their symptoms, and those considered high risk for complications are treated with antiviral drugs.

Box 1. Children at highest risk of developing serious outcomes of 2009 H1N1 influenza

Children younger than 5 years, even if previously healthy

Neurologic disorders


•Epilepsy or cerebral palsy, especially when accompanied by neurodevelopmental disabilities

•Neuromuscular disorders (e.g., muscular dystrophy)

Chronic respiratory diseases

•Moderate or severe persistent asthma

•Technology-dependent children (oxygen, tracheostomy, or a ventilator)

•Any child with impaired pulmonary function and/or difficulty handling lung secretions

Children with intellectual disability or developmental delay, especially if combined with neurologic or respiratory disorders

Immunosuppression


•Immune function deficiency

•Medications that suppress immune function (e.g., cancer treatment, transplant medications, chronic steroid use)

Congenital heart disease, especially if combined with respiratory disorder

Metabolic or endocrine disorders, especially if combined with respiratory disorder

Children undergoing long-term therapy with aspirin

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Treatment of Symptoms 

Children with mild disease are treated with supportive care of their symptoms. Rest, adequate fluid intake, and antipyretic agents are standard therapy for a child with influenza (Blosser, Brady, & Muller, 2009). Parents should be given clear parameters for signs of worsening status (i.e., chest pain, tachypnea, confusion, difficulty in arousal, and drowsiness) and directions to contact their pediatric health care provider if their child's condition appears to be worsening.

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Antiviral Treatment 

…the CDC recommends empiric antiviral treatment for high-risk children and patients with progressive or severe disease.

As previously discussed, the CDC recommends empiric antiviral treatment for high-risk children and patients with progressive or severe disease. Influenza antiviral drugs have the potential to lessen the severity and duration of illness. Antiviral treatment should be started as soon as possible, ideally within the first 48 hours of illness (CDC, 2009c). Although starting antiviral therapy in the first 2 days of illness is ideal, it has been shown to decrease respiratory failure and death from influenza even if it is started after the first 48 hours (CDC, 2009c). The standard outpatient treatment for 2009 H1N1 influenza A is oseltamivir (Tamiflu). Oseltamivir received an Emergency Use Authorization from the U.S. Food and Drug Administration (FDA) on October 30, 2009, to extend its use to children younger than 12 months (FDA, 2009). Dosing for Tamiflu is found in the Table. If a Tamiflu suspension is not available, the CDC has provided instructions to pharmacists for compounding 75 mg Tamiflu capsules into a suspension that provides 15 mg/mL (CDC, 2009c).

Table. Treatment recommendations for use of oseltamivir (Tamiflu) for treatment and chemoprophylaxis of 2009 H1N1 influenza
AgeWeightTreatment for 5 daysChemoprophylaxis
Children <3 mo 3 mg/kg/dose twice a dayNot recommended
Children ≥3 mo 3 mg/kg/dose twice a day3 mg/kg/dose
Children ≥12 mo≤15 kg30 mg twice a day30 mg once a day
Children∗16 to 23 kg45 mg twice a day45 mg once a day
Children∗24 to 40 kg60 mg twice a day60 mg once a day
Children >age 12 y and adults> 40 kg75 mg twice a day75 mg once a day

∗The CDC recommends dosing by weight rather than by age in children > 12 months and > 15 kg.

Zanamivir (Relenza), an inhaled antiviral agent, may be prescribed for patients older than 7 years who do not have a chronic respiratory disease. Zanamivir is administered by inhaler via a Diskhaler that administers 5 mg per inhalation. The dose to treat 2009 H1N1 influenza is 10 mg or two 5-mg inhalations twice a day for 5 days. Zanamivir received an Emergency Use Authorization from the FDA to extend its use to patients who have been ill with influenza symptoms for more than 2 days (CDC, 2009c).

Peramivir is an influenza antiviral agent that received Emergency Use Authorization to treat hospitalized patients with known or suspected 2009 H1N1 (CDC, 2009f). Peramivir is an unapproved drug in phase 3 clinical trials and is given intravenously to treat influenza. The Emergency Authorization limits the use of intravenously administered peramivir to patients who are hospitalized and not responding to oral or inhaled antiviral drugs or for whom intravenous administration is the only feasible route of administration. Patients and/or caregivers must be given the approved Fact Sheet for Patients and Parents/Caregivers and be informed that intravenously administered peramivir is an unapproved drug that has an Emergency Use Authorization (CDC, 2009f).

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Antiviral Resistance 

The CDC and the World Health Organization (WHO) are tracking resistance of all strains of influenza to influenza antiviral drugs. Worldwide, 267 2009 H1N1 influenza virus isolates are resistant to oseltamivir (CDC, 2010d). In the United States, 1.2% of 2009 H1N1 virus isolates (N = 63) are resistant to oseltamivir. Seasonal influenza A is usually responsive to the amantadines, with the currently circulating influenza A (H3N2) being 100% sensitive to amantadine and rimantadine (CDC, 2010c). On the other hand, the 2009 H1N1 influenza A virus does not respond to the amantadines, demonstrating 99.8% resistance to amantadine and rimantadine (CDC, 2010c). Ongoing monitoring will identify emergence of increased resistance of 2009 H1N1 to oseltamivir.

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Prevention of H1N1 Influenza 

Influenza is highly contagious and is spread from person to person by direct contact, droplet contamination, and fomites contaminated by respiratory secretions. The incubation period is 1 to 4 days, with viral shedding beginning the day before symptoms appear and continuing for 5 to 7 days. Prevention of influenza has two major components: environmental population control measures and vaccination.

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Population Control Measures 

The CDC has developed guidelines for infection control to prevent the spread of 2009 H1N1 influenza virus or any respiratory infection. The preventive measures can be taken at the individual or facility level to prevent the spread of influenza virus. Individual measures include respiratory hygiene and voluntary isolation of ill persons. Within a health care facility, measures include triage measures, environmental controls, and controlling visitor access.

Respiratory hygiene is a combination of control measures and cough etiquette that prevent the transmission of respiratory infections. The CDC recommends visual alerts to report respiratory symptoms at triage and to “Cover Your Cough” (CDC, 2009g). During times of increased influenza activity, patients should be offered a mask to contain respiratory secretions. Surgical masks may decrease the spread of influenza (Cowling, Zhou, Ip, Leung, & Aiello, 2010). Cough etiquette includes covering the mouth and nose with a tissue when coughing or sneezing (CDC, 2009g). When a tissue is not available, the mouth can be covered with the upper arm or sleeve, not the hands. Tissues should be disposed of after each use, and hands should be cleansed. Health care facilities should provide tissues and alcohol-based hand cleanser in conveniently located places.

Isolation of ill persons by staying home from school or work is critical to preventing the spread of influenza. The CDC recommends that persons with ILI stay home until they have been afebrile (temperature less than 100.0°F (37.8 °C) for 24 hours without the use of antipyretic agents (CDC, 2009h). Most patients have a fever for 2 to 4 days, thus requiring 3 to 5 days of isolation at home. The CDC recommends that patients stay at home for 24 hours after becoming afebrile even if they are treated with antiviral drugs (2009h). The goal of keeping patients with fever isolated a home is to prevent the spread of the virus, because it is thought that viral shedding occurs when the patient is febrile.

Closing of schools due to influenza is not necessary unless there is high absenteeism of students and staff that affects the functioning of the school (CDC, 2009i). The CDC has recommendations for schools based on influenza activity in the community. If flu conditions are similar to that of April 2009 to December 2009, the CDC recommends advising sick children to stay home until they are afebrile for 24 hours, discouraging those with flu-like illness from attending school events, and emphasizing respiratory etiquette and hand hygiene and routine environmental cleaning (CDC, 2009i). If flu activity is increased above 2009 levels, the recommendation is to conduct active screening for illness (fever) when children arrive at school in the morning, permit high-risk children and staff to stay home, extend the time sick people stay home to at least 7 days, advise students with sick household members to stay home, and consider school dismissal. School dismissals can be reactive (when a significant number of students and staff are ill) or pre-emptive (to prevent the spread of flu), and should be for to 7 days (CDC, 2009i).

Healthcare facilities should institute CDC-recommended pandemic influenza prevention plans when influenza activity in the local area increases. At triage patients with ILI symptoms should be identified and offered a mask to wear. Health care providers caring for patients with ILI or confirmed 2009 H1N1 influenza should wear respiratory protection, ideally a N95 mask if they are within 6 feet of a patient, and use standard contact precautions (i.e., non-sterile gloves, handwashing, gown, and eye protection) as appropriate (CDC, 2010e). Patients with ILI should be kept separate from well patients through the use of environmental measures such as partitions and separate waiting areas. Health care workers with a febrile respiratory illness should be sent home and are excluded from work until they have had 24 hours without fever (CDC, 2010e).

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H1N1 Influenza Vaccine 

The most effective way to prevent influenza is through vaccination. Influenza vaccines are unique in that the composition changes to meet the predicted circulating strains of influenza from flu season to flu season. When 2009 H1N1 circulating strain was identified as unique and not covered by the 2008/2009 seasonal influenza vaccine, the vaccine manufacturers moved into production and a vaccine was distributed to the public within a few months. To make this happen, multiple stakeholders needed to work together to protect the public from pandemic 2009 H1N1 influenza.

Seasonal influenza vaccine is manufactured in a multi-step process that begins more than a year before the flu season. Throughout the world, 131 institutions in 102 countries make up the WHO Influenza Surveillance Network, which collects samples from patients with ILI and acts as a global alert mechanism for emerging influenza strains (WHO, 2010a). Using data from the Surveillance Network, the WHO makes recommendations for the composition of the northern and southern hemisphere influenza vaccine for the following season. Seasonal influenza vaccine is composed of three influenza strains (two influenza A and one influenza B) that vary from year to year based on the predicted strains that will be circulating during the following flu season. When the strains have been determined, the process of manufacturing the vaccine begins (Box 2). Once the vaccine has been distributed and the population is vaccinated, the WHO Global Surveillance Network continues to monitor specimens to determine if the circulating strains of influenza match the composition of the seasonal influenza vaccine. The vaccine virus strains in the 2008/2009 season when 2009 H1N1 emerged were an A/Brisbane/59/2007 (H1N1)–like virus, an A/Brisbane/10/2007 (H3N2)–like virus, and a B/Florida/4/2006–like virus. In the 2009/2010 seasonal influenza vaccine were A/Brisbane/59/2007 (H1N1)–like, A/Brisbane/10/2007 (H3N2)–like, and B/Brisbane 60/2008–like antigens. 2009 H1N1 emerged too late to be included in the 2009/2010 seasonal vaccine.

Box 2. Steps in influenza vaccine-manufacturing process


1.World Health Organization Global Surveillance Network collects influenza-like illness samples from 131 sites in 102 countries

2.Influenza strains are isolated from samples at the five National Influenza Centers

3.Based on available epidemiological and virological data collected through the Surveillance Network, the World Health Organization makes a recommendation for the three viral strains in the northern and southern influenza vaccine for the following flu season

4.The identified influenza viruses are mixed with a laboratory virus to create a hybrid virus that is less dangerous and better able to grow in eggs

5.Most influenza vaccine is grown in eggs by injecting the hybrid virus into hen's eggs and incubating for 2 to 3 days

6.The vaccine virus is harvested from the egg white and killed with chemicals; the outer proteins of the virus are the antigens, the active ingredient in the vaccine

7.The production of a batch or lot takes 2 weeks; the size of the batch depends on the number of eggs a manufacture can obtain, inoculate, and incubate

8.Each batch is tested and sterility verified, which takes 2 weeks

9.The batch is diluted to a specific concentration of antigens and put into vials or syringes

10.A number of the vials and syringes are tested for sterility and to confirm protein concentration, which takes 2 weeks

The 2009 H1N1 vaccine was developed and manufactured by the same process as seasonal vaccines. As soon as the new influenza strain was identified as unique and not covered by the 2008/2009 or 2009/2010 seasonal influenza vaccine, the process of developing a vaccine began. As noted in Box 2, the process of manufacturing a vaccine is laborious and takes time. The manufacturer and the FDA conducted the same quality testing that occurs with the seasonal influenza vaccine, with each lot approved separately for release by the FDA prior to shipment (Frieden, 2009). The 2009 H1N1 vaccine began to be distributed on October 5, 2009, 5 months after the virus was first identified. The 2009 H1N1 vaccine was available as both an inactivated injectable vaccine (Fluvirin, Fluzone) and live attenuated nasal spray (Flumist).

There were non–safety-related recalls of certain lots of both the Sanofi Pasteur inactivated vaccine and live attenuated nasal 2009 H1N1 influenza vaccine because of decreased potency of the vaccine over time. The decreased potency was discovered as part of the routine quality assurance monitoring measuring stability of vaccines over the shelf life of the vaccine. Patients who had been administered 2009 H1N1 vaccine were not affected by the recall.

High-risk groups were the highest priority for the first lots of 2009 H1N1 influenza vaccine. The CDC identified high risk groups as pregnant women, caregivers of children younger than 6 months, health care workers, children aged 6 months to 24 years of age, and persons aged 25 to 64 years who have high-risk health conditions (CDC, 2009j). The CDC and state and local governments cooperated to distribute the vaccine to high-risk groups as rapidly as possible.

2009 H1N1 vaccine coverage was tracked by the CDC and state and local health departments. The estimated rate of 2009 H1N1 vaccine coverage through February 2010 for children ages 6 months to 17 years was 36.8%, higher than the 2008/2009 seasonal influenza vaccination rate of 30% (CDC, 2010f). Influenza coverage among children ranged from 21.3% in Georgia to 84.7% in Rhode Island. Four New England states (Maine, Massachusetts, Vermont, and Rhode Island) had vaccination rates greater than 60% for 6-month-olds to 17-year-olds (CDC, 2010f). These states implemented school-based vaccination campaigns, likely leading to the high rates of coverage for H1N1.

Pediatric nurse practitioners can track influenza activity, recommendations for antiviral therapy, and emerging issues with influenza at www.cdc.gov/flu/professionals.

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What Lies Ahead with the 2010-2011 Influenza Season 

The WHO Influenza Surveillance Network continues with ongoing monitoring of ILI worldwide. Based on epidemiological data provided to the WHO between September 2009 and February 2010, the WHO recommended the components of the 2010-2011 influenza vaccine for the northern hemisphere (WHO, 2010b). The three recommended viruses are:

•an A/California/7/2009 (H1N1)–like virus;

•an A/Perth/16/2009 (H3N2)–like virus; and

•a B/Brisbane/60/2008–like virus.

Because of the prevalence of circulating 2009 H1N1 vaccine during the surveillance period, A/California/7/2009 [H1N1]–like virus will be a component of the 2010-2011 trivalent vaccine. Pediatric nurse practitioners can track influenza activity, recommendations for antiviral therapy, and emerging issues with influenza at www.cdc.gov/flu/professionals.

The CDC Advisory Committee on Immunization Practices updated their recommendations in February 2010 to recommend universal seasonal influenza vaccination for all people ages 6 months and older (CDC, 2010g). There are no “high-risk” groups, and all patients should be vaccinated for influenza annually. For the 2010/2011 season, dosing of influenza vaccine will follow the same schedule as previous seasonal influenza vaccines, in which children 6 months to 8 years of age receive two doses the first year they are vaccinated, regardless of whether the children received the 2009 H1N1 vaccine (Atkinson, 2010).

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Conclusion 

Many valuable lessons were learned by public health officials and health care providers during the 2009 pandemic flu. The WHO and CDC surveillance system worked as planned to quickly detect the new influenza virus strain. The influenza vaccine manufacturers responded to develop a new vaccine in the middle of production of seasonal vaccine. The public health system worked to move the vaccine to high-risk patients as efficiently as possible. While the 2009 H1N1 influenza pandemic was not as deadly as other historical influenza pandemics, such as the 1918 flu, lessons were learned that can be used to plan for the next pandemic.

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References 

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Teri Moser Woo, Associate Professor, University of Portland School of Nursing, and Kaiser Permanente, Portland OR.

 Conflicts of interest: None to report.

PII: S0891-5245(10)00113-6

doi:10.1016/j.pedhc.2010.05.001

Refers to erratum:

  • Correction

    Journal of Pediatric Health Care September 2010 (Vol. 24, Issue 5, Page 285)

Journal of Pediatric Health Care
Volume 24, Issue 4 , Pages 258-266, July 2010

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