Felt Ill After COVID-19 Vaccine? It May Depend on Which Vaccine and Whether You’ve Had COVID-19

A image of the globe and the double helix to represent those who have opted into participate in research on COVID-19

By Daniella Coker, MPH, and Janie Shelton, Ph.D.*

A number of research present the three COVID-19 vaccines being utilized in the US — from Johnson & Johnson (J&J), Moderna, and Pfizer — are protected1,2 and efficient2,3  and provide the very best hope to beat again the pandemic.2,4 And as so many people have gotten vaccinated, it’s not possible to not discover that folks react in a different way to the vaccines. Many individuals report having no response, whereas others really feel sick sufficient to remain residence in mattress. 23andMe researchers needed to know extra about why. Is it because of the sort of vaccine or our age or what? 

To study extra about these variations we analyzed the information from greater than 100,000 23andMe consented analysis contributors and located that the second within the two-shot vaccine from Moderna produced the strongest reactions. We additionally discovered that youthful individuals and ladies tended to have stronger reactions to the vaccine than others.

However earlier than going into what our researchers discovered we needs to be clear: The unintended effects of vaccines are minimal whereas the dangers from the virus brought on by COVID-19 are extreme. This was additional confirmed by new data from the CDC.  Greater than 35 million individuals in the US have contracted the virus brought on by COVID-19, and 614,000 of them have died. Even with the rising Delta variant instances, the largest danger is remaining unvaccinated. We encourage individuals to take the recommendation of healthcare professionals, the World Health Organization, state and native public well being officers, and the CDC, and get vaccinated. 

23andMe’s researchers needed to take a look at variations in how sick individuals felt after receiving the vaccines. Now that greater than half the U.S. inhabitants has been totally vaccinated and about 60 % have had at the least one shot,5 our scientists needed to discover how individuals react in a different way to completely different vaccines, and what components could affect these variations. This examine isn’t taking a look at opposed reactions, however categorizing how individuals felt after they have been vaccinated and in contrast the diploma of “feeling sick” between three completely different vaccines.

For 23andMe’s examine, consented analysis contributors have been requested three questions: (1) What was their most up-to-date COVID-19 vaccination, (2) What signs, if any, did they expertise, and (3) How sick did they really feel afterwards. 

The majority of analysis contributors reported that their most up-to-date vaccination was their second dose of both the Pfizer (44%) or Moderna (38%) vaccine. 



General, roughly half of respondents didn’t really feel sick in any respect, 40% felt a little bit or considerably sick, and 10% felt very or extraordinarily sick. And to be clear, “feeling sick” as a response to the shot, just isn’t the identical as being clinically sick from the virus and requiring hospitalization. 23andMe scientists sought to explain and characterize this big selection of reactions to the COVID-19 vaccines. 

Listed here are a number of the key findings:

The second Moderna shot appeared to provide the strongest reactions

In comparison with the opposite vaccines, it was these individuals with a second dose Moderna vaccination who most frequently reported experiencing any signs (85%), and most frequently reported feeling both very or extraordinarily sick (18%) after their vaccination. Once more, these variations weren’t associated to medical outcomes. In different phrases, these are comparatively modest reactions to the vaccines, however the vaccines nonetheless supplied robust safety towards the virus. As well as, these reactions have been usually just for a few days after the vaccination. Whereas the severity of COVID-19 infections embody potential weeks or months of hospitalization, or dying. As well as, scientists nonetheless don’t totally know the timeline for so-called COVID-19 “longhaulers,” individuals coping with lingering signs lengthy after being contaminated.



For all vaccine varieties, fatigue, ache on the injection website, and muscle/physique aches have been essentially the most generally reported signs. But, for each symptom (besides nausea), a bigger portion of Moderna’s second dose recipients reported experiencing that symptom, in comparison with recipients of different vaccines. 



And in logistic regression fashions controlling for key demographics (age, intercourse, BMI, ethnicity, schooling, and historical past of COVID-19 an infection), having acquired a second Moderna shot was considerably related to 3x odds of experiencing any symptom and almost 1.5x odds of feeling very or extraordinarily sick (as in comparison with J&J).

So, you aren’t imagining issues — should you bought the Moderna 2nd dose and felt “underneath the climate”, you aren’t alone. Lots of people did (almost 1 in 5), however for 94.1% effectiveness towards COVID-19, we’re all applauding these of you who suffered by a couple of days of discomfort on your and the better good. 

A historical past of COVID-19 an infection related to feeling sicker 

Now, you will have heard the rumor that people who’ve had COVID-19 usually tend to really feel sick after receiving a vaccine. In response to 23andMe knowledge, that appears to be true a bigger proportion of consented analysis contributors beforehand contaminated with COVID-19 reported feeling sick, for each diploma of illness (from “a little bit” to “extraordinarily”), in comparison with these not beforehand contaminated with COVID-19. The truth is, solely a 3rd of contributors with a earlier an infection skilled no signs from their vaccine, in comparison with half of these with out a COVID-19 historical past. 



Even after controlling for the important thing demographic variables listed above, having a historical past of a COVID-19 an infection elevated your odds of experiencing any signs or feeling very/extraordinarily sick after your vaccination, each by about 30%. 

Extra and stronger reactions for girls and youthful people

Girls have been extra more likely to have any signs, have extra entire physique (systemic) signs, and customarily really feel sicker following their vaccination, in comparison with males.  

The truth is, after controlling for potential confounders, ladies have been nearly twice as doubtless as males to have felt very or extraordinarily sick.

Comparable traits have been noticed for youthful people when in comparison with older of us. These 40 years of age and youthful skilled between 2 and three whole-body signs on common, and almost 1 / 4 felt very or extraordinarily sick. Against this, these at the least 75 years previous skilled between 0 and 1 whole-body signs on common, and solely 4% felt very sick.  


These relationships between intercourse, age, and vaccine response held up, even after controlling for potential confounders.

How do the COVID-19 vaccines work?

The COVID vaccines educate your immune system to acknowledge and reply to the virus that causes COVID-19. The vaccines introduce genetic directions to make a innocent protein that’s distinctive to the virus. This triggers a two-step immune response: a primary, extra speedy and non-specific response (the innate immune response), adopted by a extra gradual, pathogen-specific response (the adaptive immune response).6

However why do some individuals really feel very sick from their COVID-19 vaccine, and others don’t really feel sick in any respect? Scientists aren’t fairly certain why that’s. Nevertheless, knowledge factors to the immune system. 

What does my vaccine response imply?

Tendencies recognized in 23andMe knowledge assist what the vaccine medical trials and different research have noticed that there are particular teams of people who find themselves extra more likely to have felt sicker from their COVID-19 vaccination. These embody: 

  • Girls7
  • Youthful individuals7, 8,9,10
  • Recipients of a second dose vaccine (in comparison with their first dose)8,9,11

Girls, as an illustration, appear to have stronger immune reactions than males. Analysis for different kinds of vaccinations, resembling for influenza, yellow fever, and hepatitis, confirmed that girls produce extra infection-fighting antibodies than males following vaccination.12 Hormonal and genetic variations between the sexes might also play a job in how the immune methods of women and men reply in a different way to vaccinations. 12,13

As we age, our immune methods are inclined to weaken.14 This may occasionally clarify why youthful adults have been usually extra more likely to report a bigger variety of and extra extreme signs following their vaccination in comparison with older adults, as seen in knowledge from 23andMe consented analysis contributors and elsewhere, together with the vaccines’ medical trials.7,8, 9, 10

By the point you obtain a second dose, your physique has already grow to be primed to acknowledge and reply to the virus that causes COVID-19, and in consequence your immune system responds quicker and stronger. 15,16 This doubtless explains why individuals are inclined to have extra extreme reactions to their second dose in comparison with their first dose.

And it might even be why 23andMe researchers observe that folks with a historical past of COVID-19 an infection additionally really feel extra sick following their most up-to-date vaccination, in comparison with these and not using a prior an infection. The virus itself is a further set off on your immune responses to kick in. A number of small research have discovered that folks with a historical past of COVID-19 an infection skilled signs extra continuously17,18 and had larger ranges of antibodies after a primary dose,19 in comparison with these and not using a historical past of an infection.

This evaluation on over 100,000 people builds upon these findings, exhibiting {that a} earlier COVID-19 an infection may not simply be associated to the variety of signs skilled following a COVID-19 vaccination, but in addition the severity of those signs.

The COVID-19 vaccines are nonetheless efficient, no matter your vaccine-related response

Though there may be some uncertainty concerning why some individuals expertise extra delicate or extreme signs following their COVID-19 vaccination, what we do know is that this: the COVID-19 vaccines are efficient, whether or not or not you felt sick after the vaccination

Knowledge from the vaccine trials confirmed that not everybody reported vaccine-related reactions; 23% from Pfizer, 18% from Moderna (second dose), and between 39% (youthful adults) and 55% (older adults) from J&J didn’t expertise any systemic reactions.8,9,10 And that is coming from the identical knowledge that demonstrated how protected and efficient these vaccines are.

Put one other means: “Even should you don’t have an disagreeable response, the vaccines are nonetheless doing their job, as a result of the true work of the immune system – and of the vaccines – takes place in the course of the second, or adaptive part of the immune response.”16 

What’s subsequent?

Analysis is ongoing to grasp why reactions to the COVID-19 vaccines differ and what these variations imply.  This work is a part of our ongoing broad analysis into COVID-19 that has included finding out how genetics performs a job in each the susceptibility and severity of COVID-19, and taking a look at different elements of the pandemic like its affect on sleep, physical activity and the way it has hit some communities harder than others. As a part of this work our, scientists are getting ready to run genetic analyses to assist reply why people react in a different way to the vaccine and what these variations would possibly imply.

*The 23andMe COVID-19 analysis workforce consists of: Adam Auton, Adrian Chubb, Alison Fitch, Alison Kung, Amanda Altman, Andy Kill, Anjali Shastri, Antony Symons, Catherine Weldon, Chelsea Ye, Jason Tan, Jeff Pollard, Jey McCreight, Jess Bielenberg, John Matthews, Johnny Lee, Lindsey Tran, Maya Lowe, Michelle Agee, Monica Royce, Nate Tang, Pooja Gandhi, Raffaello d’Amore, Ruth Tennen, Scott Dvorak, Scott Hadly, Stella Aslibekyan, Sungmin Park, Taylor Morrow, Teresa Filshtein Sonmez, Trung Le, and Yiwen Zheng. 

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