Vaccines: how men and women react

Vaccines: how men and women react differently 

Diseases, Women's Health,

Most people are surprised to learn that men and women differ in how they react to vaccines. We are living through the biggest vaccination experience of our lifetimes, so it is a good time to better understand these gender issues.

COVID vaccine reactions

Like all medical interventions, vaccinations have possible side effects. Most though are mild and temporary. For the COVID vaccines, the side effects include soreness, swelling, or pain near the vaccination site; as well as more generalized symptoms such as headache, muscle aches, fatigue, even fever and chills. But in almost in all cases, these symptoms resolve after a day or two. 

[See also in ProcuraMed: Many important people are now using 2 masks against COVID. Should you?]

Some reaction is a good sign

You might think that side effects are a bad thing. But actually, in most all cases, it’s a good sign. These symptoms show that your body is mounting an immune response to the vaccine, which means you will soon be developing antibodies and T cells to fight the viral invader if your body encounters it again. If you are on a two-shot routine, your reaction may be greater after your second shot.

Rarely, reactions are severe

Very rarely, people vaccinated get what is called an anaphylactic reaction, which is a severe, life-threatening allergic type reaction to the shot. This is very uncommon, in the neighborhood of about 11 cases per million injections (for one vaccine studied, the Pfizer). This sort of reaction is life-threatening, typically occurs within 15 minutes of the injection, but is treatable with an epinephrine injection and other medications. 

Your chance of dying from a severe allergic reaction is very small; the risk of dying in a car crash on the way to your vaccination is a greater risk! Still, it is a good idea to stay close to competent medical care—who can treat a possible allergic reaction—for the first 15 to 30 minutes after your injection.

Overall risk

Yes, there are risks of severe adverse reactions to any vaccination, including COVID, but your risk of dying from COVID (if you are unvaccinated) is much much greater than the risk of dying from a side effect from the vaccination. 

Women have more reactions

Interestingly, women are much more likely to report local reactions as well as suffer the more severe anaphylactic reactions. For the Moderna vaccine, anaphylactic reactions (among millions of injections) occurred in 19 individuals, all women. For the Pfizer vaccine, 44 of 47 anaphylactic reactions occurred in females. 

True for most vaccines

The propensity of women having  more frequent reactions is true for other vaccines as well, such as the flu vaccine. For the 2009 pandemic flu vaccine, in the 20 to 59 year age group, women were four times as likely to report allergic reactions. Another study showed that for a group of various vaccines given between 1990 to 2016, women accounted for 80% of all anaphylactic reactions.

Why women react more

There are a few theories why women react more vigorously, but the biggest factor is likely the binding of the reproductive hormones estrogen and progesterone to the women’s immune cells, which causes them to react more strongly. This fortunately results in more antibodies and more immune fighting T cells being formed in women as well. Compared with males, women make up to twice as much antibodies as men do in response to vaccines such as yellow fever, rabies, and hepatitis A and B. 

In opposition to the immune-stimulating effect of female reproductive hormones, testosterone in men seems to act as a immune suppressant. This is another reason men may have less severe side effects to vaccinations. 

Should women be cautious about vaccination?

The research shows that in general, women have stronger immune responses than men (may be one reason women live longer, and more  men die from COVID). However, this does not mean women should avoid vaccinations! This information just tells us that women should expect more side effects from vaccination, including the COVID vaccines, but that these side effects are temporary, and show that women are developing a more vigorous immune response to virus, a good thing. When you are able to take the COVID vaccine, whether you are a man or a woman, take it! Yes there are risks with the vaccine, but the risks of not taking the vaccine are much greater. 

To find a doctor, of any specialty, anywhere in Brazil, check out our website:

See also in ProcuraMed:

Many important people are now using 2 masks against COVID. Should you?

How to improve your microbiome and cut the risk of severe COVID 

Esta postagem também está disponível em: Portuguese (Brazil)

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