Dr. Mersad Alimoradi 06 Sep 2021

When it comes to COVID-19 vaccines. Men and women are different. They respond differently, they manifest side effects differently. 

This is not a complete surprise, since doctors have already established a relationship between biological gender and COVID-19 severity. Due to hormonal differences, men seem to be more likely to suffer a more serious disease course. 

For COVID vaccines, women seem to develop more side effects compared to men. Moreover, the vaccines seem to be slightly more effective in men. So, are corona vaccines different for men and women? How do they differ? Why do they differ? And what does this mean for you?

Different Vaccine Efficacy 

Before you start panicking, you should know that the difference is insignificant between males and females when it comes to COVID vaccine efficacy. 

Nevertheless, there’s a minimal difference:

  • Pfizer/Biontech: The first approved RNA vaccine from Pfizer appears to be more effective in men. The difference is negligible though. The vaccine seems to be 96.4% effective in males and 93.7% for females. 
  • Moderna: This is the second approved RNA vaccine and it works similarly to Pfizer/Biontech. This vaccine, too, seems to be more effective in men. The difference is also insignificant - 95.4% for men and 93.1% for women.

Does this difference mean anything, though? So far, it seems to be of no real value. All scientists agree that both vaccines are very effective in preventing COVID-19 infections in both males and females. The slight difference in numbers does not change that. 

False Breast Cancer Screening 

COVID-19 vaccination has been misleading doctors screening for breast cancer in patients due to enlarged lymph nodes. 

Lymph nodes are small immune glands distributed all around the body. They become bigger with infections, cancer, and vaccination. 

Enlarged lymph nodes, therefore, are suspicious, and doctors usually go further in investigating their cause. They do a biopsy or order more tests. 

After COVID-19 vaccination, lymph nodes might get enlarged in the axillary (underarm) region, which is closest to the jab. This area also happens to be one of the first affected by breast cancers. 

Some radiologists are calling for postponing breast cancer screening till after 6 weeks of the vaccine. This helps avoid any false breast cancer suspicion. 

In any case, enlarged lymph nodes after corona vaccination are a normal side effect. They actually mean that your immune system is activated, and the vaccine is working. 

Menstrual Cycle Changes 

Several women have reported having out-of-time bleeding or getting their period suddenly after the COVID-19 jab. 

This data is still strictly observational and there’s still no proven link between getting vaccinated against corona and getting your period. Nevertheless, some doctors find it a link worth investigating. 

The menstrual cycle is a complex cycle of inflammation and resolution, going on continuously in a timely fashion. 

Some authors have theorized that the reason why corona vaccines might be interfering with the menstrual cycle is that they interfere with the immune system. 

Future studies might prove that such a link does exist. Nevertheless, until then, there’s no real reason to worry. If bleeding and spotting are persistent, then you should check with your gynecologist. 

Different Side Effects 

Men and women seem to have unequal rates of side effects from COVID-19 vaccination.

A CDC analysis was done after 13.8 million corona vaccine doses confirmed this fact. In February 2021, Women made up 61% of the total of people vaccinated in the US. Nevertheless, 79.1% of the reported side effects of COVID-19 vaccines were in women.

If the rate of corona vaccine side effects were equal in men and women, you’d expect a side effects rate much closer to 61% in women. This means that the rate of side effects is significantly higher in women compared to men. 

Here are some more interesting statistical facts comparing side effects of COVID vaccines between women and men: 

  • All the patients who developed anaphylactic shock after Moderna’s vaccine were women (a total of 19 patients)
  • 44 out of the 47 reported anaphylactic shock cases after Pfizer/Biontech were in women.
  • Johnson and Johnson have reported that their single-dose vaccine seems to cause slightly more blood clots in women.  

In any case, you should know that side effects are rare in both men and women. According to the CDC and FDA, the rate of serious side effects is 0.0045%, which translates to extremely rare. 

Why the difference? 

This difference in how female and male bodies respond to the COVID-19 vaccines does not come as a surprise to doctors. 

Scientists have known for a while that the immune response is different in men and women. Women seem to produce a stronger antibody response - with corona vaccines and other vaccines as well. This stronger immune response might mean that women become more immune than men, but it might also explain why they get more side effects. 

A greater immune response means more inflammation. More inflammation means more side effects. 

Several factors play a role in causing this difference. Scientists are still studying the causes, and they believe that sex hormones might play an important role in regulating the immune system. Sex hormones have already been linked to changing the course of COVID disease. 

Should you worry? 

Doctors and health authorities do not believe that patients should worry about this. A slight difference in the immune response to corona vaccines was expected. So far, this does not seem to change anything. 

Most of the side effects reported, although a bit higher in women, are mild. Serious side effects are extremely rare in both genders

Moreover, the vaccines are almost equally effective in men and women, and the 1-2% difference does not make the vaccine ineffective. They’re still extremely successful in preventing corona in both genders

Bottom line, no, there’s no need to worry. 

Future Research 

Scientists have been working for some time on analyzing the difference in the biological response to medications between men and women. 

This might hopefully open the way to gender-based therapy, which allows doctors to be more precise in treating their patients. 

As for COVID-19, the difference between the genders does not seem to have much value on the ground. As long as you get your COVID-19 vaccine, you’re safe and you’re protected.

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About the Author:
Dr. Mersad is a medical doctor, author, and editor based in Germany. He's managed to publish several research papers early in his career. He is passionate about spreading medical knowledge. Thus, he spends a big portion of his time writing educational articles for everyone to learn.



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