Effectiveness of inactivated influenza vaccine in children aged 9 months to 3 years: an observational cohort study

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23rd November 2010 - Giving the flu jab to children under two is effective at fighting flu, according to researchers in Finland.

Under twos suffer higher rates of illness from flu than any other age group apart from over 65s - and are known to be ?super spreaders? of the virus to playmates and other family members.

Previous studies have found an annual flu jab for young children against influenza is cost effective. Less research has been done to find out the effectiveness of the vaccine in under twos. This, the researchers say, has resulted in a widespread belief that flu vaccines are not effective in this age group.

Finland is the only country in Europe to recommend flu immunisation for all children aged from six months to 35 months.

Last winter the UK brought in H1N1 jabs for children aged between six months and five years to help stop the spread of swine flu. Swine flu protection is built in to this year?s seasonal flu jab, which is only offered to children in at-risk groups from six months.
The study

Researchers from Turku University Hospital in Finland and colleagues looked at the effectivesness of flu jabs against two strains of influenza A virus and one of influenza B during the 2007-2008 flu season in Finland.

They followed 631 children and checked laboratory-confirmed flu infections for two groups of children aged nine to 40 months old who did and didn?t get the vaccine.

Overall, the effectiveness of vaccination was 66% against any influenza and 84% against influenza A.

In children younger than two, overall effectiveness of vaccination was 66%, and 79% against influenza A. The vaccines worked best when they matched the strains of flu which were circulating at the time.
UK considering the findings

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http://www.webmd.boots.com/cold-and-flu/news/20101122/study-recommended-flu-jabs-for-under-2s

 

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Re: Study recommends flu jabs for under 2s

Re: Study recommends flu jabs for under 2s

The Lancet Infectious Diseases, Early Online Publication, 23 November 2010
doi:10.1016/S1473-3099(10)70255-3Cite or Link Using DOI
Effectiveness of inactivated influenza vaccine in children aged 9 months to 3 years: an observational cohort study
Original Text
Santtu Heinonen MD a, Heli Silvennoinen MD a, Pasi Lehtinen MD a, Raija Vainionp?? PhD b, Thedi Ziegler PhD c, Dr Terho Heikkinen MD a Corresponding AuthorEmail Address
Summary
Background
Few prospectively collected data are available to support the effectiveness of inactivated influenza vaccines in children younger than 2 years. We aimed to establish the effectiveness of trivalent inactivated influenza vaccine against laboratory-confirmed influenza A and B infections in a cohort of children younger than 3 years.
Methods
In a prospective cohort study during the influenza season of 2007?08 in Turku, Finland, between Jan 14 and April 9, 2008, we assessed the effectiveness of trivalent inactivated influenza vaccine against laboratory-confirmed influenza A and B infections in children aged 9 months to 3 years. Our study was part of a clinical trial on antiviral treatment of influenza in children (ClinicalTrials.gov, number NCT00593502). The vaccine was given as part of the Finnish vaccination programme as a 0?5 mL injection. Children enrolled into our study through mailed announcements and local advertisements were examined every time they had fever or signs of respiratory infection. No exclusion criteria were used for enrolment. Influenza was diagnosed with viral culture, antigen detection, and RT-PCR assays of nasal swab specimens. Vaccination status of children was determined by parental report. We calculated the primary effectiveness of influenza vaccination by comparing the proportions of infections in fully vaccinated and unvaccinated children in the follow-up cohort.
Findings
We enrolled 631 children into our study with a mean age of 2?13 years (range 9?40 months). Seven (5%) of 154 fully vaccinated children and 61 (13%) of 456 unvaccinated children contracted influenza during the study (effectiveness 66%, 95% CI 29?84; p=0?003). In the subgroup of children younger than 2 years, four (4%) of 96 fully vaccinated children and 21 (12%) of 172 unvaccinated children contracted influenza (66%, 9?88, p=0?03). We were unable to record any adverse events associated with the vaccination of the children in our study.
Interpretation
Trivalent inactivated influenza vaccine was effective in preventing influenza in young children, including those younger than 2 years. Our findings suggest that influenza vaccine recommendations should be reassessed in most countries.
Funding
F Hoffmann-La Roche Ltd.

http://www.thelancet.com/journals/laninf/article/PIIS1473-3099(10)70255-3/abstract