1 dose of H1N1 vaccine may provide sufficient protection for infants and children

December 21, 2009

CHICAGO -- One dose of vaccine may be effective to protect infants and children and reduce transmission of the H1N1 virus, according to a study in JAMA, published online today because of its public health implications. The study will appear in the January 6 print edition of the journal.

Initial reports of 2009 influenza A(H1N1) infection in many countries have largely involved children, especially those attending school. Reports have also indicated high hospitalization rates of children younger than 5 years of age in the current pandemic, according to background information provided by the authors. "The Advisory Committee on Immunization Practices also currently recommends that infants and children aged 9 years or younger receive two doses of H1N1 influenza vaccine at least 21 days apart, based on existing experience with seasonal trivalent influenza vaccines in this age group."

Terry Nolan, M.B.B.S., Ph.D., from the University of Melbourne, Australia and colleagues assessed the effectiveness and safety of two doses of a 2009 influenza A(H1N1) vaccine in 370 healthy infants and children ages six-months to less than 9 years living in Australia. The children were randomized into groups that received a two-injection regimen 21 days apart in doses of either 15-micrograms or 30-micrograms of the vaccine.

"Following the first dose of vaccine, antibody titers of 1:40 or greater were observed in 161 of 174 infants and children in the 15-microgram group (92.5 percent) and in 168 of 172 infants and children in the 30 microgram group (97.7 percent)," the authors report. "All participants demonstrated antibody titers of 1:40 or greater after the second vaccine dose," [which means that every child achieved an antibody level considered high enough to protect against the H1N1 virus]. The researchers note that the majority of adverse reactions to the vaccine were mild to moderate in severity. The immune responses to the vaccine were strong regardless of age, baseline antibody status, or whether the child had received a seasonal influenza vaccination prior to this study.

"Our findings suggest that a single dose 15-microgram dose vaccine regimen may be effective and well tolerated in children, and may have positive implications for disease protection and reduced transmission of pandemic H1N1 in the wider population," the authors conclude.

(JAMA. 2010; 303[1]:[doi:10.1001/JAMA.2009/1911]. Available pre-embargo to the media at www.jamamedia.org)

Editor's Note: This study was sponsored by CSL Limited with funding from the Australian government's Department of Health and Ageing. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Editorial: 2009 Influenza A(H1N1) Vaccines for Children

"Even though influenza activity has decreased in recent weeks in some states, there remains the possibility of continued activity through the traditional winter influenza season and the prospect of normal winter circulation of seasonal influenza viruses," and the authors of the editorial note that this pandemic has highlighted the fact the children have no measurable immunity against the H1N1 virus.

Anthony E. Fiore, M.D., M.P.H., from the National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, and Kathleen M. Neuzil, M.D., M.P.H., of PATH, Seattle, write that children have been a primary source of illness in community outbreaks of pandemic influenza with more severe complications, hospitalizations and deaths from this virus than what is usually seen for seasonal influenza.

The editorial authors urge caution at interpretation of the results of the study. "The hemagglutinin antigen content administered to six-month-old infants and children younger than 3 years in this study was 15-micrograms, the equivalent of two doses of the 7.5-microgram vaccine currently licensed in the United States for this age group."

"The immunogenicity data presented by Nolan et al suggest that at least some children will be protected after a single 15-microgram dose of the H1N1 vaccine used in this study, but the findings cannot be generalized with confidence to all children, epidemiological circumstances in every country, or different vaccine formulations."

In conclusion, the authors write: "... it remains prudent to continue to follow current recommendations for administering two doses to infants and young children while awaiting definitive vaccine effectiveness data."
-end-
(JAMA. 2010: 303[1]:[doi: 10.1001/JAMA.2009.1929] Available pre-embargo to the media at www.jamamedia.org)

Editor's Note: Please see the article for additional information, including financial disclosures, funding and support, etc.

The JAMA Network Journals

Related Pandemic Articles from Brightsurf:

Areas where the next pandemic could emerge are revealed
An international team of human- and animal health experts has incorporated environmental, social and economic considerations -- including air transit centrality - to identify key areas at risk of leading to the next pandemic.

Narcissists love being pandemic 'essential workers'
There's one group of essential workers who especially enjoy being called a ''hero'' during the COVID-19 pandemic: narcissists.

COVID-19: Air quality influences the pandemic
An interdisciplinary team from the University of Geneva and the ETH Z├╝rich spin-off Meteodat investigated possible interactions between acutely elevated levels of fine particulate matter and the virulence of the coronavirus disease.

People who purchased firearms during pandemic more likely to be suicidal
People who purchase a firearm during the pandemic are more likely to be suicidal than other firearm owners, according to a Rutgers study.

Measles outbreaks likely in wake of COVID-19 pandemic
Major measles outbreaks will likely occur during 2021 as an unexpected consequence of the COVID-19 pandemic, according to a new academic article.

The COVID-19 pandemic: How US universities responded
A new George Mason University study found that the majority of university announcements occurred on the same day as the World Health Organization's pandemic declaration.

Researchers find evidence of pandemic fatigue
A new study from the USC Leonard Davis School of Gerontology shows that the behavioral responses to COVID-19 differed by age.

Excessive alcohol consumption during the COVID-19 pandemic
The full impact of COVID-19 on alcohol use is not yet known, but rates have been rising during the first few months of the pandemic.

How fear encourages physical distancing during pandemic
Despite guidelines plastered on the walls and floors of grocery and retail stores encouraging customers to maintain six-feet of physical distance during the pandemic, many do not.

COVID-19 pandemic and $16 trillion virus
This Viewpoint aggregates mortality, morbidity, mental health conditions, and direct economic losses to estimate the total cost of the pandemic in the US on the optimistic assumption that it will be substantially contained by the fall of 2021.

Read More: Pandemic News and Pandemic Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.