Vaccines against influenza A (H1N1) pandemic

The World Health Organization (WHO) has reported, as of September 2009, that the influenza A (H1N1) influenza pandemic has originated >300,000 laboratory-confirmed cases and 3917 deaths in 191 countries. It is recognized that pandemic vaccines have their greatest impact as a preventive strategy when administered before or near the peak incidence of cases in an outbreak. Therefore, vaccination campaigns should be in place when influenza A (H1N1) 2009 vaccines are available. We undertook this study to provide updated information on clinical evaluation of influenza A (H1N1) vaccines and review recommendations for influenza A (H1N1) vaccination campaigns and public health policy.

The following methods were used: 1) review of registry at ClinicalTrials.gov. 2) search of PubMed Central (PMC) for influenza A (H1N1) vaccine. 3) review of recommendations of WHO, Mexican Health Secretariat (SSA) and Advisory Committee on Immunization Practices (ACIP) on influenza A (H1N1) vaccination campaigns.

Until October 1, 2009 there were 11 available influenza A (H1N1) candidate strains provided by WHO Global Influenza Surveillance Network. ClinicalTrials.gov registers 45 phase I and II clinical trials evaluating immunogenicity and safety of influenza A (H1N1) vaccines. Preliminary results support administration of a single dose and use of adjuvants. Main recommendations of WHO, SSA and ACIP include epidemiologic considerations, objectives, definition of target groups and reinforcement of other mitigation measures.

The present pandemic of influenza A (H1N1) has shown mild to moderate severity. Vaccination strategies in Mexico will have the objective of decreasing severe outcomes, slowing transmission, protecting groups at increased risk of infection, complications, or death, and preventing overload of health services. Control of the pandemic should include reinforcement of other non-pharmacologic measures of mitigation and, importantly, an adequate strategy of social communication.