Every year, the state health departments and the Ministry of Health promote flu vaccination campaigns. But why this immunization effort against the virus Influenza is required annually? Should people get vaccinated every year? And who should get vaccinated?
According to infectious disease specialist Ana Helena Gremoglio, carrying out annual campaigns against the flu has basically two reasons. One of them is the fact that the virus Influenza to have many different strains, as with the new coronavirus.
This year, for example, the vaccination campaign against the flu offers immunizers that protect against three types of the virus: H1N1, H3N2 and Iflu B. The initiative was launched on the day April 4. Mobilization D-day is scheduled for April 30th.
“The influenza vaccine is annual because the viruses that circulate are different, and it needs to be redesigned for a person to create immunity. It is different from other vaccines in which the viruses do not change as much, such as MMR and hepatitis”, explains the doctor.
Due to the presence of variants, each year vaccines are adapted to protect people against the most common strains. Sentinel hospitals collect samples from people using the instrument swab (which collects material samples). These materials are analyzed by central laboratories and, with this, the main circulating strains are identified. This mapping subsidizes the production of vaccines for the following year.
Another reason for annual campaigns is the fact that flu vaccines do not maintain their effectiveness for more than six months. As the time of greatest circulation of the virus is during the winter, campaigns are generally launched at the beginning of the second quarter of the year, in April.
“Immunity to influenza it takes six months. It is at the time of greater viral transmission that we have to have more antibodies. It is designed on a platform so that maximum immunity is achieved at the same time of greater viral circulation and colder temperatures, when people tend to be more crowded”, comments the infectologist.
Ana Helena Gremoglio considers that flu vaccination campaigns should be expanded in view of the drop in immunization rates since 2014. Last year, for example, the flu vaccination campaign reached 72.1% of the target audience, when the goal was to apply the doses in 90% of the segments.
“Vaccination campaigns exist, but far from what they should happen. They should be daily, reinforcing the importance, safety and efficacy of vaccines. Since 2014, prevention campaigns have been put aside. Sometimes people think that it is better to invest in care than in prevention, but in prevention it is cheaper and more efficient”, says the doctor.