The FDA authorized a third COVID-19 vaccine Feb. 27, this one from Johnson & Johnson.
A look at how the new vaccine compares to Moderna's and Pfizer's:
What's the same:
- All three vaccines are very effective. Pfizer and Moderna's vaccines were both more than 94 percent effective at preventing COVID-19 in late-stage trials. Johnson & Johnson's was 66 percent effective at preventing COVID-19, but completely prevented hospitalizations and death from the virus, according to The Washington Post. It was also 85 percent effective against severe COVID-19 at least 28 days after vaccination, The Wall Street Journal reported. Experts told the Post that comparing the three vaccine's efficacy rates is difficult because the trials were conducted at different times during the pandemic (Pfizer and Moderna's trials took place before the emergence of virus variants) and in different countries with different variants and transmission rates.
What's different:
- The way it works to protect against COVID-19. Both Moderna's and Pfizer's vaccines use mRNA to carry genetic instructions for cells to produce antibodies that fight COVID-19. But Johnson & Johnson's vaccine is a viral vector vaccine, meaning it uses an adenovirus, which is a virus that has been genetically altered so it doesn't cause illness but can still cause the immune system to build defenses against a certain virus, according to The New York Times. The adenovirus carries DNA into cells and, once inside, the DNA causes production of the coronavirus' spike protein, which then triggers an immune response that can protect against COVID-19, the Journal reported.
- The number of doses. Both Moderna and Pfizer's vaccines require two doses, spread out between three or four weeks, to get full protection. But Johnson & Johnson's vaccine requires just one dose.
- Who's old enough to get a shot. Pfizer's vaccine is authorized for everyone 16 years and older. Both Moderna and Johnson & Johnson's vaccines are approved for use in people 18 and older.
- How it's stored. Johnson & Johnson's vaccine can be kept in an ordinary refrigerator for three months, the Times reported. Both Pfizer and Moderna's vaccines have to be frozen, though Pfizer recently gained FDA approval to keep its vaccine at higher temperatures than the ultralow temperatures it previously required. Moderna's vaccine spoils after one month if not kept frozen, the Times reported.
- Adverse reactions to the shot. Johnson & Johnson's vaccine seems less likely to trigger allergic reactions, the Journal reported. Johnson & Johnson has received just two preliminary reports of cases of severe allergic reactions from the vaccine. The CDC has said severe reactions from COVID-19 vaccines are rare.
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