The growing number of COVID-19 vaccines becoming available—and even more on the horizon—raises the question: Should you be picky about which COVID-19 vaccine you get?
To start, know that experts generally recommend that the public takes whichever vaccine they’re offered right now. “This is a race between the virus and getting vaccines into people. The longer someone waits to get vaccinated, the better chance the virus has to get a variant or a mutation,” Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases, said previously. So, the sooner people get vaccinated—with whichever vaccine they can get—the better, he said.
But there are some significant differences between the available vaccines that are worth knowing about ahead of time. Here’s what you need to know about the three vaccines available in the U.S. right now.
How many doses do you need?
Both the Pfizer-BioNTech and Moderna vaccines were developed as two-shot systems, meaning they require an initial injection and a booster several weeks later. The Pfizer injections are given 21 days apart and the Moderna doses are given 28 days apart.
But the J&J vaccine is a one-dose vaccine, which makes it logistically much easier to administer to large groups of people. “That’s a significant advantage,” Raymond Tellier, M.D., associate professor in the division of infectious diseases at McGill University Health Centre, tells SELF.
How effective are they?
The Pfizer-BioNTech and Moderna vaccines, which both rely on mRNA technology to initiate a protective immune response in the body, offer almost identical protection against a symptomatic COVID-19 infection. In clinical trials including almost 44,000 participants, the Pfizer vaccine was 95% effective at preventing symptomatic COVID-19 seven days after the second dose compared to the placebo. And in a clinical trial with almost 30,000 participants, the Moderna vaccine was 94.1% effective at protecting against symptomatic coronavirus infections 14 days after the second dose.
As for the J&J vaccine, which uses an altered adenovirus vector rather than mRNA technology, the vaccine is 66% effective at preventing moderate-to-severe COVID-19 infections and 85% effective against severe disease. Those numbers come from an FDA review of clinical trials conducted in eight countries and including nearly 44,000 participants. But the exact efficacy of the vaccine varied by country. In the U.S., the shot was 72% effective, but in Latin America efficacy fell to 66% and only then to 57% in South Africa.
It can be difficult to directly compare the results from the different vaccines because they were studied in different countries where different coronavirus variants may have affected the results. But the most important takeaway is that all three vaccines show significant efficacy at reducing hospitalization and deaths due to COVID-19.
But preventing symptoms is only one piece of containing the pandemic. Ideally, these vaccines would also prevent asymptomatic infections and make it harder for the virus to spread from person to person. “It’s unclear whether you also have protection against asymptomatic infection,” Dr. Tellier says. The data suggest that this could be possible to some degree, but it’s unlikely that the vaccines offer complete protection from asymptomatic infections, he said.
Because of those unknowns—and the fact that many, many people have yet to be fully vaccinated in the U.S.—it’s still important to wear a mask and observe social distancing guidelines even after you get the vaccine.
What kinds of side effects do they cause?
These three vaccines, like basically every medical drug or treatment, can come with some temporary side effects. The side effects are normal signs that your body’s building protection against the virus, according to the Centers for Disease Control and Prevention (CDC).
Some of the most common side effects associated with the Moderna and Pfizer vaccines include pain at the injection site, fatigue, headache, fever, and muscle pain. These tend to last a few days after the first dose. But they can be more severe, possibly even impacting your ability to do daily tasks, after the second dose. Still, they are temporary, generally lasting a few days.
For the Johnson & Johnson vaccine, the most common side effects are similar and include pain at the injection site, fatigue, nausea, headache, and muscle aches, the FDA says. These side effects tend to be mild to moderate and only last a day or two.
How long do the vaccines take to work?
“This isn’t known with great precision,” Dr. Tellier says.”Typically, after a vaccine it takes about two weeks for antibodies to become detectable; these would usually correlate with protection.” And the CDC currently says it likely takes about two weeks after getting vaccinated against COVID-19 to get the full effect.
We know that the Pfizer and J&J vaccine regimens take around 28 days to reach their full effect. Moderna may take a bit longer—the clinical trials measured the Moderna vaccine’s efficacy two weeks after the second shot, so after a total of six weeks.
However, there is some early evidence from studies in England and Israel that a single shot of the Pfizer/BioNTech vaccine may offer a substantial amount of protection on its own. And some experts previously floated the idea of delaying some people’s second shots and instead prioritizing getting as many people one shot as possible. However, Dr. Fauci said previously (and reiterated this month) that the U.S. will not break from its current approach.
How long does their protection last?
Unfortunately, we don’t know yet how long protection from any of the vaccines will last, Jesse Erasmus, Ph.D., a molecular virologist at the University of Washington School of Medicine, tells SELF.
Understanding how long the vaccines’ protection actually lasts needs to be studied in real time, Dr. Erasmus says, so these studies take much longer to complete. The Pfizer clinical trial, for example, won’t be officially finished until 2023.
But based on the data we have from ongoing clinical trials so far, we know the protection is likely to last at least three-to-four months. As the trials continue, we’ll keep learning more.
How effective will these vaccines be against emerging coronavirus variants?
The answer to this question depends on the exact variant and the mutations it carries. For instance, all three vaccines have some reduction in efficacy against the B.1.351 variant, first identified in South Africa, Dr. Erasmus says.
But a reduction in efficacy doesn’t mean the vaccines are useless. “Even though there is a reduction [in protection], it should still be more than enough [to prevent hospitalization and death],” Dr. Tellier explains. And even if you do get COVID-19 after getting vaccinated, you will likely have a much milder experience than if you hadn’t gotten the vaccine. (Remember, all three vaccines significantly prevented hospitalization and deaths.)
As other variants continue to emerge, it’s likely we will see updated vaccines and boosters to bolster our immunity. In fact, Moderna just shipped samples of a booster shot developed to protect against emerging variants to the National Institutes of Health for study last month, according to a press release from the company. So it’s very possible that your first COVID-19 vaccine won’t be your last, Dr. Tellier says.
So which COVID-19 vaccine should I get?
Despite the differences between the vaccines, experts agree that the best vaccine is the one you can get the soonest. “Get the one you can get now,” Dr. Tellier says.
Even though the J&J vaccine isn’t quite as effective as Moderna and Pfizer, it still offers substantial protection against COVID-19 compared to placebo. And, most importantly, “they all are going to protect against severe disease to a very high degree,” Dr. Erasmus says.