Are the reactions worse this year?

Last week I got my annual flu shot. I can’t remember a year when I experienced any of the known side effects from the flu shot. Usually, I get my hang of it and go about my business. But this time it was different. I was tired and had pain in my arm for about three days after that.

It turns out that I was not alone. After seeing anecdotal evidence for what Atlantic writer Amanda Mull called an “extra spicy” hit, I called three infectious disease doctors to ask if there really were any more intense reactions this year. Their responses have been edited and condensed for clarity.

Julia Craven: Is the flu shot “worse,” meaning people might experience more serious side effects this year?

Arnold Monto, professor of epidemiology at the University of Michigan: People are made aware of side effects because they have been given COVID vaccines, which are known to produce side effects. They are more likely to look for or perceive side effects that they would not have bothered to experience [notice] before. A reasonable percentage of people have arm pain [from the flu vaccine], but beyond that the percentage of people who have any side effect is quite low. This data does not really fluctuate from year to year.

All flu shots are quadrivalent this year, that is, they contain four strains influenza virus. How might this affect the symptoms?

Nasia Safdar, Medical Director of Infection Prevention at the University of Wisconsin Hospital: It really shouldn’t. Quadrivalent vaccines are available and most of us have been receiving them for years. There is a high dose influenza vaccine that is recommended for older people, and the tenderness in the arms may be a bit higher and it takes a bit longer to recover.

William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center: The entire influenza vaccine manufacturing industry has been moving towards quadrivalent vaccines for the past decade. And this year, everyone is there in all its formulations. This is great since each vaccine will protect against four strains of the influenza virus. Quad is associated with about the same range of side effects as the old trivalent vaccine. Nonetheless, I am very curious about it and look forward to getting more data as the vaccination season unfolds.

Could the side effects that some people report experience be stronger because many of us have avoided getting sick for over 18 months?

Safdar: I saw no supporting data.

Schaffner: The answer is we just don’t know because we haven’t had a precedent for it. There is also speculation that, once the flu virus returns, will it cause more widespread illness because we have been less experienced with the flu in the last season. Again, there is no clear indication that this is the case, but it’s an interesting question. And I’m afraid the answer is we’ll have to wait and see.

Are there fears this flu season will be worse?

Safdar: We fear it could be worse because earlier this year and last year we didn’t have much flu season, possibly because schools weren’t in person and everyone was in hiding and stayed at home. There was that wasted opportunity to build immunity, which happens every year, and so this year, yes, it just could be worse.

Rising: A lot of people have speculated that since we didn’t really have a flu season last year, this winter could be a catch-up season. But it’s only an hypothesis. One thing I think we can say with enough confidence is that if we see a flu season, it won’t be soon. If we were to witness an early flu season around Thanksgiving, we would see the start of it all happening now.

When should people get the flu shot this year?

Safdar: Earlier is better. September and October are good times. It takes two weeks for your body to generate antibodies after the vaccine, so you don’t want to leave it too late. Sometimes people think they should wait until they see evidence of the flu circulating and it’s probably too late.

Why is it important to get the flu shot even though you are still taking COVID precautions, like masking yourself and not eating inside?

Schaffner: The flu is another nasty respiratory virus that affects people of all ages. It affects the elderly and people with underlying illnesses of all ages. And every year, children, including perfectly healthy children, die from the flu. Anything we can do to prevent this, while mitigating the impact on the healthcare system, which is already affected by COVID, is great.

The most common reason people don’t get the vaccine is that they don’t think the vaccine is very good. We recognize that its effectiveness varies from year to year, depending on the virus and the composition of the vaccine. But most people don’t realize that even if you get the flu after getting the vaccine, you’re much less likely to get serious illness; it makes your illness milder. You are less likely to require hospitalization, admission to an intensive care unit, and you are less likely to die.