Despite recent media hype over the supposed effectiveness of one dose of the Moderna and Pfizer/BioNTech COVID-19 vaccines, the FDA and government scientists aren’t budging from the two-dose approach, officials said at a press briefing on Friday.
Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, argued that one dose doesn’t assure a durable immune response, and thus leaves potential for people with poorer immune responses to become incubators for escape variants.
Commenting largely about an Israeli study published in The Lancet, which appeared to show that one dose of the Pfizer/BioNTech vaccine is 85% effective, Fauci called the results “interesting,” but added, “we will stick with the scientifically documented efficacy and optimal response of a prime followed by a boost” of mRNA vaccine.
“We’re not criticizing the study,” he added. “We do want to follow up on this.”
However, Andy Slavitt, the White House senior advisor for COVID-19 response, did not mince words in defending the U.S. government’s two-dose approach.
“There are studies all the time, there are preprints all the time, there is real-world evidence all the time. One study, even though it may look attractive, it may capture a headline … it isn’t always what it appears to be,” he said. “It’s important to understand we’re not going to be persuaded by one study that happens to grab headlines.”
Fauci also noted important limitations to the data, which the authors acknowledged, such as that “subjects were younger and healthier” than in other studies and the study shed no light on how long protection with one dose would last, “as most of the subjects received their second shot,” he said.
When deciding on the two-dose strategy, Fauci stressed durability of immunity as a major factor.
“If you look at the difference between the degree, the intensity of response after a first dose and compare it to after a second dose, the second dose has 10 times higher levels of neutralizing antibodies,” he said.
Even in the event of a five- to six-fold diminution of antibodies induced by an mRNA vaccine candidate against something like a COVID-19 variant, “it’s still in the range of protection,” he added.
“The response following the boost is so high that though [overall] efficacy is diminished to 50% [against the South African variant], it still had good efficacy against severe disease,” he noted.
And if individuals have suboptimal responses, “because of immunological pressure” on the virus, they could “theoretically … be selecting for variants.”
Vaccine Safety Affirmed
During the same briefing, CDC Director Rochelle Walensky, MD, discussed an early Morbidity and Mortality Weekly Report release, which a low rate of anaphylaxis during the first month of COVID-19 vaccination.
In fact, Walensky said that the 4.5 anaphylaxis cases per million doses was “a rate similar to what we’ve seen in other commonly used vaccines.”
She cited statistics from the CDC’s v-safe, a post-COVID-19 vaccination smartphone-based monitoring program, which found that of the 1.6 million people enrolled, about 71% reported injection site pain, a third reported fatigue, and about 30% reported headache.
Of the 113 deaths reported, 65% of those were among long-term care facility residents, which Walensky noted was “consistent with the background rate in this demographic.”
She urged the public to “know the facts and not the myths about vaccine safety,” and said CDC and FDA would continue to closely monitor events and report them as needed.
Walensky also said that CDC is convening a 3-day national forum on COVID-19 vaccines, beginning on Monday, where government and non-government partners can share information about building trust, with practical real-world experience on increasing vaccination in community settings.
Regarding vaccine distribution, Slavitt discussed the current severe weather plaguing much of the southeastern U.S., and said that while there is a backlog of about 6 million vaccine doses representing about 3 days of delayed shipping, many states should be able to cover with existing inventory.
He added that 1.4 million doses are already in transit, and all backlogged doses should be delivered within the next week. In addition, UPS and FedEx will be able to support Saturday deliveries, and the government is working with jurisdictions to see which are able to take these deliveries.
“Vaccines … will be ready to ship out as soon as the weather allows,” Slavitt said.