Newswise — Children in the USA and Canada are being vaccinated against influenza
without adequate proof that it will work, concludes a study published in this week’s
issue of The Lancet.
Most immunisation campaigns target people aged 65
years or older. The USA and Canada have recently started vaccinating children, including
those aged 6 to 24 months, in the hope of reducing disease spread, admissions and visits
to hospitals, deaths of elderly relatives, complications (such as ear infections and
pneumonia), absences from school, and parental loss of workdays and over-prescribing of
antibiotics. However, there is no evidence that vaccinating children can achieve these
goals.
Tom Jefferson (Cochrane Vaccines Field, Italy) and
colleagues identified and assessed 25comparative studies that evaluated the efficacy
(reduction in laboratory confirmed case) and effectiveness (reduction in symptomatic
cases) on influenza vaccines in healthy children aged 16 years or younger.
Vaccines of live viruses with weakened infectivity
had 79% efficacy and 38% effectiveness in children older than two years compared with
placebo or no immunisation. Inactivated vaccines had a lower efficacy (65%) than live
weakened vaccines, and in children aged two years or younger they had similar effects to
placebo. Effectiveness of inactivated vaccines was about 28% in children older than two
years. Vaccines were effective in reducing long school absences but had little effect on
other outcomes such as hospital stays and lower respiratory tract disease, when compared
with placebo or no intervention. However, the authors note that these conclusions are
based on a small number of studies.
Dr Jefferson concludes: “We have identified a
large dataset showing reasonable quality evidence of efficacy of influenza vaccines in
children age 2 years or older, especially for twodose live attenuated vaccines. However,
we noted a striking difference between efficacy and effectiveness of vaccines because of
the large proportion of influenza-like illness caused by agents other than influenza
viruses. This is an important point in the decision to immunise whole populations.
Immunisation of very young children is not lent support by our findings. Although a
growing body of evidence shows effect of influenza on admissions and deaths of children,
we recorded no convincing evidence that vaccines can
reduce mortality, hospital admissions, serious complications and community transmission of
influenza.”
Please remember to cite The Lancet.
