Vaccine Science

For some people, COVID-19 can be a mild illness. However, it can cause serious complications or death for others — including healthy people. The vaccine is important in helping to prevent or reduce the effects of COVID-19. Prevention is key to helping end the pandemic. Experts say that 75% to 85% of the population needs to get vaccinated to achieve community immunity, also known as herd immunity.

Learn from our public health care experts

What is an mRNA Vaccine?

Learn more to help make your decision to get a COVID-19 vaccine. Our experts developed this to briefly explain how mRNA vaccines work and answer your questions about their safety and effectiveness.

An animation of a circle surrounding a woman after receiving her vaccination

Myths and Misconceptions

UF Health expert Dr. Michael Lauzardo discusses myths and misconceptions about the vaccines and how best to inform yourself.

Dr. Michael Lauzardo Answers Questions About Vaccine Safety and Effectiveness

Is one of the COVID-19 vaccines better than the other?

The FDA applies the same review process to all vaccines, regardless of the manufacturer.

  • The FDA fully approved the Pfizer BioNTech vaccine on August 23, 2021. This vaccine was renamed Comirnaty.
  • The FDA approved the Moderna COVID-19 vaccine for individuals over the age of 18 on January 31, 2022. This vaccine was renamed Spikevax.

FDA full approval was based on continuing clinical evidence of the vaccine’s safety and efficacy. Moderna has been shown to be at least 93% effective, and Pfizer has been shown to be at least 88% effective.

FDA has issued an Emergency Use Authorization for Johnson & Johnson’s Janssen COVID-19 vaccine. This EUA is limited to adults 18 and older who cannot take other approved COVID-19 vaccines. It has shown to be at least 71% effective.

How many doses of the vaccine will I need?

It depends on which vaccine is available and provided to you. Although some immunity might be provided with the first dose of a two-part vaccine, the research used to look at how the two-dose vaccines worked shows how effective they are with both doses, not just one. The one-dose Johnson & Johnson vaccine reduces the number of appointments you will need to attend but offers similar immunity.

How soon after getting vaccinated am I protected?

After you are fully vaccinated, you should develop immunity in about one to two weeks, but the specific timeline for any COVID-19 vaccine will depend to some extent on which type of vaccine it is.

If I have already had COVID-19, should I still get the vaccine?

Yes, we recommend you get the vaccine even if you’ve already had COVID-19. Studies show that having COVID-19 might offer some natural protection from reinfection. But those studies also show the protection might not last very long. The vaccines target the virus’ ability to infect people. Getting the vaccine reduces your chances of reinfection and avoiding severe COVID-19 medical complications.

If you’ve had COVID-19, you might delay vaccination for up to 60 days after your diagnosis. Reinfection during this period is uncommon.

Flu and other vaccines

  • The CDC and health experts now suggest you can get the flu shot and the COVID-19 vaccine on the same day. It is recommended that you receive the injections in different arms.
  • The COVID-19 vaccine does not take the place of other vaccines. It is a good idea to be up-to-date on pneumonia and flu vaccines in addition to COVID-19. Please talk to your health care provider about which vaccines are recommended for you.