Health

How do the vaccines work?

  • There are three main types of COVID-19 vaccines: messenger RNA (mRNA), protein subunit and vector.
  • All three vaccine types either deliver, or cause our bodies to make, harmless proteins like the ones found on the surface of the COVID-19 virus.
  • The vaccine teaches our immune system to recognize the virus. After we are vaccinated, if we are exposed to the virus, our immune system recognizes, attacks and blocks the virus.
Icon of gloved hand blocking COVID-19 particles

Three Main Types of Vaccines

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    mRNA

    mRNA is a molecule that tells our bodies to make proteins. mRNA in the COVID-19 vaccine tells our cells to make harmless proteins just like those on the virus. The Pfizer and Moderna vaccines work this way.

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    Protein Subunit

    Protein subunit vaccines, such as the Novavax vaccine, contain harmless pieces of proteins unique to the COVID-19 virus.

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    Vector

    Vector vaccines, like the J&J vaccine, use another virus that has been made safe to deliver material that tells our cells to make harmless proteins unique to the COVID-19 virus.

What to expect when you get vaccinated

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    The Pfizer, Moderna and AstraZeneca vaccines are given as two shots in the upper arm muscle, three or four weeks apart.* The Johnson and Johnson vaccine is given as one shot in the upper arm muscle.

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    Typically, it takes about two to four weeks after the second shot for the immune system's protection to fully respond to the vaccination.

  • Icon demonstrating spread of COVID-19

    Even after the vaccination, you might be able to pick up the virus, carry it and give it to others. Infection prevention measures in public and among unvaccinated people are still very important.

*The number of times vaccines made by other companies are given and the way they are given vary. A third dose is now available for immunocompromised individuals. Contact a healthcare provider for more information.  

Are the vaccines safe?

Although the Pfizer, Moderna and Johnson & Johnson vaccines were developed in a faster than usual process, they were extensively tested for both safety and efficacy. All three vaccines have met Food and Drug Administration (FDA) safety standards and will be carefully monitored to detect any problems or side effects.
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Do the vaccines work?

  • Based on clinical trials, the Pfizer, Moderna and Johnson & Johnson vaccines are extremely effective at preventing infection from the virus and/or preventing serious disease, hospitalization and death from COVID-19.*
  • The trials so far show the vaccines are equally effective across age, gender, race and ethnicity subgroups.
  • The clinical trials were conducted with a diverse group of participants, including people of Asian, Black, Hispanic/Latinx and Native American descent.**
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*As additional clinical trials are completed, we will know more about the efficacy of other vaccines. **Among the Pfizer participants, 5% were Asian, 10% were Black, 26% were Hispanic/Latinx and 1% were Native American. Among the Moderna participants, 4% were Asian, 10% were Black, 20% were Hispanic/Latinx and 3% were of other descent. Among Johnson & Johnson participants in the US, 6% were Asian, 13% were Black, 15% were Hispanic, and 1% were Native American.

IMPORTANT VACCINE FACTS

  • Icon demonstrating vaccine will not cause COVID-19

    Fact one

    You will not get COVID-19 from the vaccine.

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    Fact two

    The vaccine will not change or damage your genetic information.

  • Icon of COVID-19 prevention measures

    Fact three

    Even if you are vaccinated, you should still wear your mask, frequently wash your hands and maintain physical distance to help keep everyone safe.

  • Doctor vaccinating female patient

    Fact four

    The Pfizer, Moderna and Johnson & Johnson vaccines are all equally important in stopping the spread of COVID-19.

  • Fact five

    If you are pregnant, trying to become pregnant now or want to get pregnant in the future it is still safe for you to get the vaccine.

Check with your state and local health departments for information on when the vaccines will be available to you. Visit hopkinsmedicine.org/coronavirus for more information on the vaccines.
Learn more about the COVID-19 vaccines