The campaign of flu vaccination has begun and like every year, around the flu vaccine, some doubts arise. Among the most consulted is what side effects has the immunization.
The first thing that the Ministry of Health highlights in its document ‘Questions and Answers about vaccination against influenza’ is that many clinical studies have confirmed its safety and, in the world, hundreds of millions of doses are administered.
But, like any drug, it has its side effects. The most frequent after administration of the vaccine is discomfort and/or pain at the injection site. These local reactions usually last less than 48 hours and rarely interfere with the normal life of vaccinated people.
Other reactions such as fever, malaise or muscle aches may also appear after vaccination, which begin in the first 6-12 hours and usually last 1-2 days.
The same document also explains that flu shots cannot cause flu. And as for the most common reactions that vaccinated people have, remember that they are considerably less serious than the symptoms caused by the actual disease.
Regarding why there are people who have catarrhal symptoms after vaccination, Health explains that there are several reasons. It may be because numerous respiratory viruses coexist (rhinovirus, respiratory syncytial virus, parainfluenza virus, adenovirus…), in addition to the flu virus, which spread and cause illness during the flu season.
It must also be taken into account that, from the moment the vaccine is received, two weeks for the body to develop immune protection. “It is possible to have been infected by the influenza virus immediately before being vaccinated or during the two weeks after vaccination, so a person could have the flu despite having been vaccinated,” the document recalls.
Also, some people can be infected by a flu viruses other than those listed in the vaccine or may not be adequately protected due to advanced age or health status. “The ability of vaccines to protect a person against the flu depends, to a large extent, on the coincidence of the viruses selected to make the vaccine and those that circulate in that season, and on the ability of the immune system to generate immune protection. », they point out from the Ministry.