Babies under two have second the highest rates of flu, after the elderly. Giving them the flu vaccine has been found to be effective in preventing influenza. Researchers from Turku University Hospital, Finland wrote in the medical journal The Lancet Infectious Diseases that vaccination guidelines should be revised.
The authors added that babies under two also tend to spread the flu to other members of the household as well as the community.
Although studies had shown a financial benefit for immunization of young children, there are so few that have examined how effective vaccines are in very young kids that most people eventually believed that they were ineffective.
If there is no evidence about, showing the benefits of immunizing very young children, it is not surprising that national health authorities do not recommend it, the authors wrote. The only country in Europe to recommend universal flu vaccinations for individuals aged from 6 months to 35 years is Finland.
Terho Heikkinen and team set out to determine how effective the trivalent inactivated flu vaccine was during the 2007-2008 Finnish flu season. The trivalent vaccine has antigens that give the human immunity against one influenza virus B strain and two influenza A strains.
They compared data on 631 children aged 9 to 40 months, some of whom who had laboratory-confirmed influenza A and B infections. Some of the children had been vaccinated against flu and others had not.
They found that the vaccination was 66% effective at protecting against flu in general, and 84% against the A viruses.
For babies under the age of two years, the vaccine’s effectiveness was 66% overall, and 79% against the A viruses.
33 of the 71 cases of influenza was caused by mismatched influenza B viruses; the vaccine had not been designed to protect against those strains.
The researchers wrote:
- “Our findings accord with recent studies showing a clear correlation between the effectiveness of the vaccine and the match between the vaccine and circulating strains…[suggesting] that the clinical effectiveness of influenza vaccination is far more dependent on the match of the vaccine antigens than the age of the recipient.”
No adverse events in the immunized children were detected. According to national Finnish data, there were 38 adverse events, consisting mostly of eczema and fever, out of 63,048 children who were given at least one dose.
The authors concluded:
- “These results provide clear evidence for effectiveness of the inactivated influenza vaccine even in the youngest children during seasons with normal influenza activity and a good antigenic match between the vaccine and the circulating strains of influenza…Our findings suggest that influenza vaccine recommendations should be reassessed in most countries.”
Mark Steinhoff from Cincinnati Children’s Hospital Medical Center, Cincinnati, USA, in an Accompanying Comment say that the next step is to carry out a large European, multicenter, multiyear, randomized influenza immunization trial on under twos, “to assess the cost-effectiveness of a strategy for universal immunisation for influenza in children and the broader effect for such a strategy on families and communities.”
Santtu Heinonen MD, Heli Silvennoinen MD, Pasi Lehtinen MD, Raija Vainionpää PhD, Thedi Ziegler PhD, Dr Terho Heikkinen MD
The Lancet Infectious Diseases, Early Online Publication, 23 November 2010
doi:10.1016/S1473-3099(10)70255-3
Written by Christian Nordqvist