The incubation period of influenza is within the range of one to four days, but the formation of antibodies which provide protection against influenza takes approximately 14 days. A simple mathematical calculation thus tells us that the peak of the epidemic may arrive before we develop immunity to the virus, even with today’s application of the vaccine. If a patient is vaccinated against flu during the period of the epidemic, the vaccine may not provide the expected protection. On the other hand, however, it is not possible to state that the vaccine will be entirely ineffective: effectiveness depends on the length of time during which the organism is exposed to the flu virus after vaccination. As a result doctors recommend that we are vaccinated at the beginning of the season and that only patients in risk groups in individual cases are vaccinated during the time of the flu epidemic.
In connection with the first media reports of deaths as a consequence of contracting influenza, many people have realised that it would be better to be vaccinated. Unfortunately the vaccine may not work at such a late stage, due to the epidemiology of influenza.