Because so many governments, particularly those in developed countries such as the USA and UK, are strongly recommending vaccination against flu, the general perception is that vaccination works and is protective. However, this assumption has been challenged in an analysis performed by Dr. Tom Jefferson and his colleagues at Cochrane Vaccines Field, an organization based in Italy that was founded to gather evidence on vaccines and their effects. The staff there is compiling a “Vaccines Register” comprising all relevant studies on the effectiveness, safety and economics of vaccines. In an analysis of the data published with flu vaccines, Dr. Jefferson reported (1) that in children under 2 years of age, inactivated virus vaccines had “the same field efficacy as placebo (2) and in healthy people under 65 vaccination did not affect hospital stay, time off work, or death from influenza and its complications (3).” No evidence was found of an effect in patients with asthma or cystic fibrosis, but inactivated virus vaccines did result in a 39% reduction in the incidence of exacerbations after three to four weeks in those with chronic obstructive pulmonary disease (4-6).
In his review in the British Medical Journal (1), Dr. Jefferson concluded with the following observations and comments:
“Public policy worldwide recommends the use of inactivated influenza vaccines to prevent seasonal outbreaks.
Because viral circulation and antigenic match vary each year and non-randomised studies predominate, systematic reviews of large datasets from several decades provide the best information on vaccine performance.
Evidence from systematic reviews shows that inactivated vaccines have little or no effect on the effects measured.
Most studies are of poor methodological quality and the impact of confounders is high.
Little comparative evidence exists on the safety of these vaccines.
Reasons for the current gap between policy and evidence are unclear, but given the huge resources involved, a re-evaluation should be urgently undertaken.”
As more data become available, there should be further clarity on the question of whether flu vaccines are effective or not and how the results obtained with nasal spray vaccines containing weakened live virus compare with those from intramuscular injections of inactivated virus.
References
1) Jefferson, T. (2006) Influenza Vaccination: Policy versus Evidence. Brit. Med J. 333, 912-915
2) Smith. S., Demicheli. V., Di Pietrantonj, C., Harnden, A.R., Jefferson, T, Matheson, N.J., et al. (2006) Vaccines for Preventing Influenza in Healthy Children. Cochrane Database Syst. Rev. (1): CD004879.
3) Demicheli, V., Rivetti, D., Deeks, J.J., Jefferson, T.O. (2004) Vaccines for Preventing Influenza in Healthy Adults. Cochrane Database Syst. Rev. (3): CD001269.
4) Cates, C.J., Jefferson, T.O., Bara, A..L, Rowe, B.H. Vaccines for Preventing Influenza in People with Asthma. (2003) Cochrane Database Syst. Rev. (4): CD000364.
5) Poole, P.J., Chacko, E., Wood-Baker, R.W.B., Cates. C.J. (2006) Influenza Vaccine for Patients with Chronic Obstructive Pulmonary Disease. Cochrane Database Syst. Rev. (1): CD002733.
6) Bhalla, P., Tan, A., Smyth, R. (2000) Vaccines for Preventing Influenza in People with Cystic Fibrosis. Cochrane Database Syst. Rev. (1): CD001753.
Christopher J. Jones, M.Sc., Ph.D.
Comments on this entry are closed.