America is skeptical of the ‘dark horse’ COVID vaccine others abroad can’t get enough of

The number who’ve been fully vaccinated with Novavax, the latest vaccine to receive approval from US health officials: only 6,278.

The traditional protein-based vaccine, approved by US health officials in July, was intended to win the hearts and minds of Americans who were hesitant to receive mRNA COVID vaccines Pfizer and modernclaiming that the technology was too new to be considered safe.

“For those waiting for a COVID-19 vaccine built on a different technology, now is the time to get vaccinated,” CDC Director Dr. Rochelle Walensky said this summer.

But for the 20% of Americans who remain unvaccinatedhesitancy about the safety of mRNA vaccine technology was likely just an excuse, experts say, as Novavax was formulated using the same technology as the flu vaccine—and uptake is still dismal.

However hesitant Americans are about Novavax, for whatever reasons, the situation is quite the opposite elsewhere. The vaccine has been approved in 38 other countries, including Australia, France, Ireland, Italy, Korea, and the UK, according to the World Health Organization. And Japan and Australia have approved the vaccine for use as a booster dose, according to the Journal of the American Medical Association.

“It’s been attractive for a long time,” Dr. John Swartzberg, a professor at the Division of Infectious Diseases and Vaccinology at the University of California, Berkeley’s School of Public Health, told Fortune, adding that the manufacturing issues delayed its US debut.

“What excited some people about it is the fact that it’s very similar to a lot of vaccines produced in the past,” Swartzberg said. “Protein vaccines have been used for decades. For some people, that gives them a degree of comfort, based upon emotion and not science.”

Novavax has the potential to offer longer, broader protection than current mRNA vaccines, Dr. Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP), told Fortune.

But more data on the vaccine is needed to determine the length of protection it offers, as well as its performance against Omicron subvariants.

“I think it could be a better vaccine,” Osterholm said, although he cautioned that, in the early days of mRNA COVID vaccines, society had “unbridled expectations that ultimately didn’t pan out,” such as the vaccines preventing infection.

Like mRNA vaccines, Novavax protects against severe COVID outcomes like hospitalization and death. But it doesn’t prevent infection or transmission, according to Yale Medicine.

Maryland-based Novavax began developing its COVID vaccine in 2020, during Operation Warp Speed, but manufacturing difficulties slowed progress. Countries started granting the vaccine approval in November.

In the US, the two-dose shot series is approved for those 12 and older, with shots occurring three to eight weeks apart. Side effects are similar to mRNA COVID vaccines and include tenderness, pain, and/or swelling at the injection site, fatigue, muscle pain, joint pain, headache, nausea, vomiting, and/or fever, according to Yale Medicine. As is the case with mRNA COVID vaccines, myocarditis—a rare form of heart inflammation—has been reported, although rarely.

Dr. Bali Pulendran, professor of microbiology and immunology at Stanford University, told Fortune he isn’t sure why the US hasn’t yet approved Novavax for use as a booster, giving those who’ve received a two-dose mRNA series another option, aside from the newly approved Omicron mRNA vaccines.

The US Food and Drug Administration did not immediately respond to Fortune’s question as to why the US has not approved the vaccine for use as a booster, although other countries have.

“It’s a terrific vaccine, and I hope people get access to it if they wish to,” said Pulendran.