Flu season is approaching…
Annual vaccination against influenza A and B viruses is the most effective method of preventing influenza. A new vaccine is available for the current season and includes four strains: H1N1, H3N2 and two B viruses. Our office provides both the quadrivalent vaccine which gives protection against four viruses and the high dose vaccine for those who are 65 years and older.
The influenza vaccine reaches maximal effectiveness about 2 weeks after vaccination and persists for at least 6-8 months. Except for soreness at the injection site, adverse reactions to the vaccine are uncommon. It is not possible to get infected with the influenza virus from the inactivated vaccine.
Some Frequently Asked Questions answered by the CDC (Centers for Disease Control and Prevention)
How long does a flu vaccine protect me from getting the flu?
Multiple studies conducted over different seasons and across vaccine types and influenza virus subtypes have shown that the body’s immunity to influenza viruses (acquired either through natural infection or vaccination) declines over time. The decline in antibodies is influenced by several factors, including the antigen used in the vaccine, the age of the person being vaccinated, and the person’s general health (for example, certain chronic health conditions may have an impact on immunity). When most healthy people with regular immune systems are vaccinated, their bodies produce antibodies and they are protected throughout the flu season, even as antibody levels decline over time. Older people and those with weakened immune systems may not generate the same amount of antibodies after vaccination; further, their antibody levels may drop more quickly when compared to healthy people.
For everyone, getting vaccinated each year provides the best protection against influenza throughout flu season. It’s important to get a flu vaccine every year, even if you got vaccinated the season before and the viruses in the vaccine have not changed for the current season.
Will this season’s vaccine be a good match for circulating viruses?
It’s not possible to predict with certainty if the vaccine will be a good match for circulating viruses. The vaccine is made to protect against the flu viruses that research indicates will likely be most common during the season. However, experts must pick which viruses to include in the vaccine many months in advance in order for vaccine to be produced and delivered on time. And flu viruses change constantly (called drift) – they can change from one season to the next or they can even change within the course of one flu season. Because of these factors, there is always the possibility of a less than optimal match between circulating viruses and the viruses in the vaccine.
Over the course of the flu season, CDC studies samples of circulating flu viruses to evaluate how close a match there is between viruses used to make the vaccine and circulating viruses.
One of the ways that helps CDC evaluate the match between vaccine viruses and circulating viruses is with a lab process called ‘antigenic characterization’. Results of antigenic characterization testing are published weekly in CDC’s FluView.
The match between the vaccine viruses and the circulating viruses is one factor that impacts how well the vaccine works.
Can the vaccine provide protection even if the vaccine is not a “good” match?
Yes, antibodies made in response to vaccination with one flu virus can sometimes provide protection against different but related viruses. A less than ideal match may result in reduced vaccine effectiveness against the virus that is different from what is in the vaccine, but it can still provide some protection against influenza illness.
In addition, it’s important to remember that the flu vaccine contains three or four flu viruses (depending on the type of vaccine you receive) so that even when there is a less than ideal match or lower effectiveness against one virus, the vaccine may protect against the other viruses.
For these reasons, even during seasons when there is a less than ideal match, CDC continues to recommend flu vaccination for everyone six months and older. Vaccination is particularly important for people at high risk for serious flu complications, and their close contacts.
Can I get vaccinated and still get the flu?
Yes. It’s possible to get sick with the flu even if you have been vaccinated (although you won’t know for sure unless you get a flu test). This is possible for the following reasons:
- You may be exposed to a flu virus shortly before getting vaccinated or during the period that it takes the body to gain protection after getting vaccinated. This exposure may result in you becoming ill with flu before the vaccine begins to protect you. (About 2 weeks after vaccination, antibodies that provide protection develop in the body.)
- You may be exposed to a flu virus that is not included in the seasonal flu vaccine. There are many different flu viruses that circulate every year. The flu vaccine is made to protect against the three or four flu viruses that research suggests will be most common.
- Unfortunately, some people can become infected with a flu virus the flu vaccine is designed to protect against, despite getting vaccinated. Protection provided by flu vaccination can vary widely, based in part on health and age factors of the person getting vaccinated. In general, the flu vaccine works best among healthy younger adults and older children. Some older people and people with certain chronic illnesses may develop less immunity after vaccination. Flu vaccination is not a perfect tool, but it is the best way to protect against flu infection.
Why is the higher dose vaccine available for adults 65 and older?
Human immune defenses become weaker with age, which places older people at greater risk of severe illness from influenza. Also, ageing decreases the body’s ability to have a good immune response after getting influenza vaccine. A higher dose of antigen in the vaccine is supposed to give older people a better immune response, and therefore, better protection against flu.