Does it matter which COVID-19 vaccine you get?

The Moderna and Pfizer COVID-19 vaccines have many similarities. But is one better than the other?

The Moderna and Pfizer COVID-19 vaccines have many similarities. But is one better than the other? (Deposit Photos/)

At this time last year, most Americans had not yet heard of a strange cluster of pneumonia cases affecting people in Wuhan, China. A full year later, scientists have identified and isolated the virus that causes this disease, COVID-19, and have developed multiple successful vaccines to protect against it. At the same time, the human toll has been immense: more than 350,000 Americans have died from the disease, and countless others are still recovering from infections.

These vaccines, then, are crucial. But which should you get?

The answer is straightforward: both vaccines that are currently available have been shown to be safe and effective. In other words, it does not matter which approved vaccine a person gets, and either option is much better than no shot at all.

Currently, two vaccines have been granted emergency use authorizations from the FDA. Both vaccines, created by Pfizer/BioNTech and Moderna, are mRNA-based and require two shots. In clinical trials, both have been shown to be around 95 percent effective at preventing laboratory-confirmed COVID-19 illness.

But for now, the question of which vaccine to get is moot.

“The most common answer you’re going to hear is that we’re not going to have a choice for many, many months, and you’re going to take whatever’s available,” says Susan Kaech, professor and director of the NOMIS Center for Immunobiology and Microbial Pathogenesis.

Moderna’s and Pfizer’s vaccines both rely on mRNA (messenger RNA) to provide our cells with a blueprint to make copies of an important coronavirus protein. Our immune system recognizes the protein as foreign, learns how to destroy it, and remembers it in case it sees the real coronavirus in the future. The ingredients in the two vaccines differ slightly, as well as the microscopic packaging in which the mRNA sequences come. Because of this, the Pfizer vaccine must be stored at a very low temperature, which limits who can access that vaccine.

Several other vaccines candidates are being tested in clinical trials currently. Two, from AstraZeneca and Johnson & Johnson, use a weakened adenovirus (a type of very common virus) to get the instructions for coronavirus proteins into humans. A third, from Novavax, injects a lab-made version of a coronavirus protein along with an adjuvant to stimulate the immune system. Phase 3 clinical trial results for the AstraZeneca vaccine showed it to be up to 90 percent effective in preventing disease, slightly less effective than the two mRNA vaccines.

“If you did have a choice, I think I would probably still go with the ones that are showing 95 percent efficacy, but I would certainly be happy to have the other adenoviral-based vaccine if that was what was available to me,” Kaech says. “I wouldn’t skip getting a vaccine because the Moderna or the Pfizer vaccines weren’t available.”

Getting vaccinated presents two benefits, Kaech says. Either of the authorized vaccines will protect against severe cases of coronavirus disease. Most vaccines also prevent the illness from being transmitted, though it is not yet known whether any of the coronavirus vaccines stop people from being infected with and then spreading the virus. Preliminary evidence suggets that the AstraZeneca and Moderna vaccines may reduce transmission. A more mild case of the disease may lower the risk for long-term symptoms or COVID long-haulers, she adds, so even if you get sick after receiving a vaccine, you’ll be better off than if you hadn’t gotten vaccinated.

Barring specific allergies, Americans don’t generally get to choose the specific vaccine they receive for a given disease. When you take your child to the pediatrician to get a vaccine for diphtheria, tetanus, and whooping cough, for example, you may not know that there are six different pediatric vaccines licensed for that purpose. Individual doctors offices (or groups of them) pick which vaccine to order ahead of time. Some places allow you to choose which flu shot you get, especially if you’re allergic to eggs, but many only offer one type.

We’re not used to having a choice of vaccine, which is why multiple options of a coronavirus vaccine may be confusing to some, Kaech says.

Still, she notes, it’s a good thing that there are more vaccine candidates being developed and tested. A greater diversity of vaccines will reduce the pressure on manufacturers and vaccine distributors, with the result of increased availability.

“If at the end of a year from now, we have 10 vaccines that are protective, I think it would be just as important as having two highly protective vaccines today,” says Kaech, “because it’ll make the global distribution a lot easier.”

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