We are fortunate to have multiple COVID-19 vaccines that are safe and effective. If a vaccine is offered to you, take it.

"Get whichever vaccine is available to you for which you do not have a contraindication," says David Brett-Major, MD, MPH.

For instance, if you're allergic to certain vaccine ingredients, avoid that particular vaccine. The Johnson & Johnson (Janssen) and Moderna vaccines are authorized for ages 18 and older, while Pfizer's vaccine is authorized for people ages 16 and older.

How well they work

After two doses, the Pfizer and Moderna vaccine had efficacy rates of 95% and 94%, respectively. The Johnson & Johnson vaccine's efficacy rate with a single dose was 72% in the U.S. 

All three vaccines prevented hospitalizations and deaths extremely well in trials. Any vaccine that turns a deadly disease into a mild one is something to celebrate.

Plus, vaccinations are critical to avoiding more infections (and mutations). Critical care anesthesiologist Daniel W. Johnson, MD, writes, "If we get everyone vaccinated swiftly, the virus will not have the opportunity to mutate into new variants that are untouchable by existing vaccines."

One dose or two?

The mRNA vaccines (Moderna and Pfizer) require two doses, spaced weeks apart. The second Pfizer vaccination is given three weeks after the first shot. Moderna is four weeks. Johnson & Johnson was approved for a single shot. We do not yet know what the best approach will be for booster doses over time.

You are considered fully vaccinated two weeks after your final dose.

Side effects

The Johnson & Johnson vaccine seems to cause fewer acute side effects than the Moderna or Pfizer vaccines, based on their respective clinical trials. Most side effects go away after a few days.
 

*Johnson & Johnson, after the only dose among all vaccine participants
**Pfizer, after second dose among participants 18 to 55 years old
***Moderna, after second dose among participants 18 to 64 years old