Moderna and Pfizer are already developing COVID-19 vaccine boosters. Do we need a third shot?

Last Updated: May 28, 2021 at 7:30 a.m. ET First Published: May 25, 2021 at 11:27 a.m. ET

By

Jaimy Lee

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Vaccine makers say immunity to the virus can begin to wane after six or eight months. But more clinical data is needed, experts say

Pfizer's COVID-19 vaccine vials are seen at a mobile vaccination clinic in Los Angeles.

AFP via Getty Images

It looks like Americans may need to roll up their sleeves for a COVID-19 booster shot, though vaccine makers and federal officials are still trying to detect how long immunity to the virus lasts. 

In the latest race to the regulatory finish line, Pfizer Inc. PFE, 0.30% is testing its experimental COVID-19 booster shot in combination with its 20-valent pneumococcal conjugate vaccine in older adults, while Moderna Inc. MRNA, 3.16% told investors this month that a mid-stage clinical trial showed its investigational booster can help protect against the serious B.1.351 and P.1. variants.

Moderna and Pfizer both developed two-dose, mRNA vaccines with similar rates of real-world effectiveness.

The COVID-19 vaccines developed by these companies, as well as the Johnson & Johnson JNJ, 0.44% shot — the third vaccine to be authorized in the U.S. — are all considered very effective, especially when it comes to preventing hospitalization and death, but it’s still unknown how long they can protect people against the virus.

See also: Booster dose of COVID vaccines to be given to U.K. volunteers in new trial

“We do not have data on when to expect waning immunity leading to breakthrough infections,” Dr. Stephen Hoge, Moderna’s president, told investors, according to a FactSet transcript of a May 6 earnings call. “But we do know that there is a raging pandemic, that reinfections will happen at some point, and the best way to ensure that we do not have renewed outbreaks in well-vaccinated countries is to boost and maintain the highest possible levels of neutralizing antibodies.”

Moderna and Pfizer have recently said immunity can start to wane between six to eight months after getting the second shot of their vaccines. Dr. Peter Marks, a Food and Drug Administration official, estimates that vaccine-induced immunity is around one year, according to public remarks reported by CNBC. 

“I would project that it’s actually going to be longer than that,” Dr. Mark Mulligan, director of NYU Langone Health’s Vaccine Center, said in a May 3 interview. “It might be a year or even more. But in all likelihood, for boosting of the magnitude of the antibody levels and other immune responses, boosters will be needed.”

If SARS-CoV-2 becomes an endemic virus, as some medical experts have predicted, boosters are one way to keep people protected and also address gaps in immunity caused by powerful variants like B.1.351, first detected in South Africa, and the P.1 first identified in Brazil that are thought to lessen the effectiveness of these vaccines.

However, at this point, it’s all speculation. There is no medical consensus about whether booster shots are necessary to ensure continued protection against this virus or even what the durability of immunity to this virus is. 

“There’s absolutely no evidence that we need a booster shot of anything,” Dr. Carlos del Rio, an infectious-disease physician and executive associate dean of the Emory University School of Medicine, said April 28. “The most important thing to do is to get vaccinated right now. Whether you’re going to need a booster shot, we’ll worry about that later.”

The case for-or-against booster shots 

The only data about the length of vaccine-induced immunity, which likely takes into account antibody titer levels and T-cell response, is limited at this time.

“We do not know precisely when we will need to boost,” Dr. Anthony Fauci, President Joe Biden’s chief medical advisor, said Tuesday during a White House briefing.

One study found that the Pfizer vaccine, which was developed with BioNTech SE BNTX, 3.00%, has a 91.3% efficacy rate among clinical-trial participants six months after they got the second dose. Other research indicates that people who are enrolled in the Phase 1 clinical study for Moderna’s vaccine still had antibodies six months after getting the second shot. 

“It’s likely that it’s not just a single booster but that this would be a repeated event over the next several years,” Mulligan said. “If we achieve broad enough vaccination to shut down virus transmission and have the pandemic die out, great. But we’re so far [from] that right now.”

About 39% of people in the U.S. are fully vaccinated, as of Tuesday, according to the latest data from the Centers for Disease Control and Prevention, though vaccination rates in the U.S. have been slowing for weeks.

Other experts disagree with the push for boosters, citing a lack of data. 

Cornell University virologist John Moore recently told Axios “it’s not proven that we need boosters yet. Whereas it’s appropriate to plan for boosters, you’ve got to look at whether there’s a corporate agenda behind this.”

Del Rio instead predicts a future in which the U.S. will have the virus under control, and Americans may need a COVID-19 booster to travel to certain countries, much like how a yellow fever vaccine or booster is recommended or required for travel to certain Central and South American and African countries.

“I suspect that if there’s a variant in India, and you decide to travel to India, you will be told, as part of your travel, you’re going to have to take this,” he said. 

Are boosters another billion-dollar opportunity for vaccine makers?

COVID-19 vaccines are already a booming business for drug makers, and boosters are part of the corporate strategy going forward. (Moderna executives mentioned their booster shot dozens of times on their most recent earnings call.)

Pfizer and BioNTech expect their vaccine to generate $26 billion in revenue this year, while Moderna just reported its first-ever billion-dollar sales quarter.

While the U.S. government has not announced any purchases of COVID-19 booster shots, other countries have. Australia, Israel, and Switzerland have already inked deals with these drug makers to buy millions of booster doses for 2022.

Pfizer anticipates it will get data for its booster candidate in July, with plans to file for authorization that same month and then get a regulatory okay in the U.S. sometime in 2021.

The company is developing two types of shots: one functions like a third dose of its currently available vaccine, aiming to boost immunity among participants from its Phase 1 clinical trial in the U.S., and the other uses a modified mRNA sequence. It announced the booster/pneumococcal conjugate vaccine study this week. 

Moderna is testing three types of boosters:

• A booster that acts like a third dose to its original two-dose vaccine.
• A booster that specifically aims to address the B.1.351 and P.1 variants. (Both of these variants are of particular concern to Moderna and Pfizer because the companies ran their pivotal Phase 3 clinical trials at a time before those variants had been identified as concerning.)
• A booster that is made up of a 50/50 mix of its original vaccine and the booster targeting the B.1.351 variant.

What about other vaccine makers?

J&J has not yet shared any longer-term data about its vaccine’s immune response, though executives have noted that the company plans to assess whether there is a need to develop a booster.

However, some Wall Street analysts have said it’s easier to develop boosters for mRNA and protein-based vaccines than adenovirus-based vaccines like the J&J shot. (Novavax Inc. NVAX, -2.03% is an example of a company developing a protein-based COVID-19 vaccine candidate.)

Sanofi SNY, 0.96%, which has previously reported some delays moving its COVID-19 vaccine through development, recently hinted to investors that its still-investigational single-dose COVID-19 shot may have more value as a booster. The vaccine candidate is expected to move into Phase 3 clinical trials, and it will also be tested in a booster-specific study.

That said, boosters and vaccination in general doesn’t need to be a one-size-fits-all model for every single person.

The U.S. could test out a different approach for booster shots that evaluates an individual’s antibody levels to assess whether or not they need a booster shot at all, said Dr. Michael Mina, an assistant professor of epidemiology at the Harvard T.H. Chan School of Public Health. This is because immunity shows up differently in different people, based on factors like age and overall health.

“It would be super easy to set up, and it could be voluntary,” Mina said. “Do you want a booster? Do you want to see if you need a booster? To get there, we would really want to start building correlates of protection, meaning: what is the antibody level that we feel good as a physician or as a public health agency saying, if you’re at this level, you’re probably still protected.”