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Last updated February 10, 2021. 3 minute read

Can you spread COVID-19 after getting vaccinated?

You cannot get COVID-19 from the vaccine, but you may develop symptoms that make you feel unwell. The COVID-19 vaccines are very effective at protecting you against COVID-19, but scientists don’t know if they also prevent infection.

Dr Chimene Richa Md Written by Dr. Chimene Richa, MD
Reviewed by Dr. Steve Silvestro, MD

Before 2020, the leading cause of death in Americans was heart disease. However, after the onset of the global coronavirus disease 2019 (COVID-19) pandemic, COVID-19 has soared past heart disease to become the leading killer in the United States (Woolf, 2021). Fortunately, we now have very effective vaccines available in the country to help combat this disease’s spread.

Vitals

  • You cannot get COVID-19 from the vaccine, but you may develop symptoms that make you feel unwell.
  • The Moderna and Pfizer-BioNTech mRNA vaccines are very effective at protecting you against COVID-19 disease, but scientists don’t know if they also prevent infection.
  • Even after getting the vaccine, it is possible to get the COVID-19 virus, never develop symptoms of COVID-19, and still pass the infection on to others—scientists are still researching the likelihood of this happening.
  • Continue to practice social distancing measures, wear a mask, etc., even after receiving the vaccine.

Can you infect someone else after getting the vaccine?

The answer to this question has two parts. 

First of all, you cannot get COVID-19 from the COVID-19 vaccine and then pass it on to others. The mRNA vaccines, like the ones from Moderna or Pfizer-BioNTech, only carry the viral genetic material that codes for specific proteins. They do not contain live virus particles, so they cannot give you SARS-CoV-2, the virus that causes COVID-19. It is normal to have side effects like arm soreness, headaches, fatigue, and muscle aches after getting the vaccine—these are signs that your immune system is activated.

What about getting COVID-19 from other people after you get the vaccine and then transmitting it to others—this answer is a bit more complicated. You may have heard that the clinical trials on these vaccines showed high effectiveness. That’s true—they are 94.5% or 95% effective (depending on whether it is the Moderna or the PfizerBioNTech version, respectively) at preventing people from developing the COVID-19 disease (FDA, 2020a; FDA, 2020b). They measured this by counting the number of people who developed symptoms of COVID-19. They did not include people who were infected with the virus but had no signs of illness. In fact, around one in six people infected with the SARS-CoV-2 virus do not develop any symptoms—in other words, they are asymptomatic (Byambasuren, 2020). 

Scientists don’t know yet if the vaccine protects you against asymptomatic infection with the COVID-19 virus. You could potentially become infected but never develop symptoms and then pass it on to others unwittingly. 

Additionally, it takes time for your immune system to be fully “trained” to respond to the COVID-19 virus. It takes several weeks from the time of the first vaccine dose to maximal protection. Theoretically, if you were exposed to the COVID-19 virus after you received the vaccine but before your body has had the chance to be fully armed against the virus, you could get COVID-19 and then pass it on to others. 

Just because you received the vaccine does not mean that you can throw caution to the wind. Until scientists know more about the vaccine’s ability to protect against infection, you need to continue practicing social distancing measures, wearing a face mask, etc., even if you have received the vaccine. 

Both the Moderna and Pfizer/BioNTech vaccines are very effective in preventing you from getting sick with COVID-19. We don’t know whether they can protect you from getting infected with the SARS-CoV-2 virus while remaining symptom-free, thereby allowing you to potentially pass the virus along to others who could get sick with COVID-19.