The immunogenic effects of influenza A against the influenza A vaccine at the time of approval could only be estimated on the basis of studies in which the rate of those vaccinated with presumably protective antibody titres was determined. In such studies, adjuvanted A / H1N1 vaccines triggered the formation of antibodies in about nine out of ten vaccinated persons in titers that are associated with protective effect. But how high was the protective effect for the normal population during the epidemic? The question of the clinical effectiveness of the vaccine can only be answered after wave of disease. The Robert Koch Institute (RKI) in Berlin has now done this with two epidemiological studies on the clinical effectiveness of vaccination with the AS03-adjuvanted A / H1N1 vaccine Pandemrix® (Epid Bull 21; 2010: 198–201). The results are based on the joint surveillance data of the RKI and the National Reference Center for Influenza.
Study 1 was (test-negative) case-control study for which data from 6,195 patients with influenza symptoms were available (PCR as laboratory test of samples from the nasopharynx and case information). In the case series method used in study 2, the data from 73,280 cases that were reported between the 44th and 53rd calendar week were evaluated. The vaccination status was known, usually also the date of the vaccination.
First important result: After vaccination, it apparently takes an average of eleven days for immunity to develop. This is because the rate of positive laboratory tests in vaccinated people decreased significantly from day twelve after immunization. For the under 14 age group, the scientists found clinical effectiveness of 84 percent in the case control study and 85 percent in the study evaluated using the case series method. For those older than 13 years of age, the clinical effectiveness was 74 percent in the case-control study and 68 percent in Study 2. The results were statistically significant in each case. The researchers' conclusion: The clinical effectiveness of the A / H1N1 vaccine is age-dependent, as is known from vaccines against seasonal influenza. And: single vaccination with the adjuvanted A / H1N1 vaccine reduces the risk of disease to significantly less than 50 percent.
Dr. rer. nat. Nicola Siegmund-Schultze