To help speed up Covid-19 vaccinations across the United States, especially among high-risk older adults, one idea continues to surface: Postpone second doses. The idea is that delaying second doses for those who have already received a first dose would allow for more people in prioritized groups to get at least one dose if they haven’t received it already.
“We get down the list faster if we do all those first doses,” Marc Lipsitch, professor of epidemiology at the Harvard T.H. Chan School of Public Health, told CNN on Monday.
“My view is that the weight of the evidence suggests that we would probably save more lives by delaying second doses than by insisting on the schedule that was tested in the trials,” he said.
Yet not all experts agree that changing dosing schedules is a good idea.
“We have two problems with that. The first – they may not get fully protected and that might accelerate the rate of variants taking over and causing us much more trouble in the future,” William Haseltine, chair and president of the global think tank ACCESS Health International, said during an appearance on CNN’s New Day on Monday.
“Secondly, we really don’t know if delaying the second dose for a long time is going to give you the same degree of protection,” he said. In other words, there’s not much research as Covid-19 vaccines were developed only recently.
Meanwhile, as debates around delaying second doses continue in the United States, so do a slow vaccine rollout, more Covid-19 deaths and the spread of newly identified coronavirus variants that appear to be more transmissible.
Getting second doses is priority, but ‘there is some wiggle room’
It is still recommended for people to get their second dose of Covid-19 vaccine on time, Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention, said during a virtual White House briefing on Monday.
“Until we have further data,” Walensky said, people should continue to follow the data from trials by continuing the schedule of receiving two doses 21 days apart for the Pfizer/BioNTech vaccine and 28 days apart for the Moderna vaccine. Those are the two vaccines currently authorized for emergency use in the United States.
“The policy is that we certainly want everyone who gets a first dose to get their second dose,” Dr. Anthony Fauci, chief medical advisor to President Biden and director of the National Institute of Allergy and Infectious Diseases, said during Monday’s briefing.
But also on Monday, during a meeting of the International AIDS Society, Fauci said that if you’re late by just a couple of weeks there isn’t a cause for concern. “There is some wiggle room,” he said. “It’s not the end of the world if you delay a little bit. If you want to delay it by six months, that’s different.”
Delaying second doses would go against the vaccine schedules that have been authorized under the US Food and Drug Administration.
In January, the FDA made clear that it does not plan to change coronavirus vaccine dosing schedules – and for such adjustments to occur, the vaccine manufacturer would have to specifically ask the agency to adjust authorization.
CNN confirmed with the FDA in January that if a manufacturer requests a change to its emergency use authorization, the manufacturer would need to submit data to the FDA supporting the requested change.
Some experts argue that there is evidence to support a possible change.
‘We need to have a really comprehensive review and discussion of this’
Lipsitch of Harvard University is in favor of spreading out vaccine doses in a larger population rather than doubling doses for half of that population. “If you can get at least half the benefit, then it’s better to spread it out,” he said.
For the Pfizer/BioNTech vaccine, called BNT162b2, data suggest that the vaccine has 52% efficacy after just one dose and then provides 95% protection against Covid-19 after two doses.
In a Phase 3 trial that was conducted at 99 sites in the United States, data suggest that Moderna’s vaccine mRNA-1273 showed efficacy after the first dose.
But trials haven’t been conducted to test single doses of mRNA vaccines.
Some emerging evidence in a pre-print paper, posted to the online server medrxiv.org on Monday, found that after getting just one shot of a Covid-19 vaccine, people who were previously infected with the virus tended to have antibody levels that were at or above those of people who had gotten both doses but never been previously infected. The study does not specify which vaccine participants received.
For many other vaccines – such as the chickenpox, HPV and measles, mumps and rubella vaccines – their second-dose booster shots are given several months later, Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told CNN on Monday.
“At this point, everything we know about vaccines suggests that actually the protection may be enhanced by giving a booster several months after the first dose,” said Osterholm, who was a coronavirus adviser to the Biden transition team.
Osterholm pointed to a letter-to-the-editor that published in the journal Clinical Infectious Diseases last week, in which Dr. Stanley Plotkin of the University of Pennsylvania and Dr. Neal Halsey of Johns Hopkins University calculated about how many people could be protected against Covid-19 if single doses are given.
The researchers hypothesized, “suppose that 1 million people are to be vaccinated but only 1 million doses are available. If two doses are given to each vaccinee and the efficacy is 95%, 475,000 people will be protected. If single doses are given and the efficacy is 80%, 800,000 people will be protected.”
Osterholm said that getting people vaccinated – even with just one dose for now – remains urgent as more coronavirus variants circulate, including the B.1.1.7 variant first identified in the United Kingdom, B.1.351 first identified in South Africa, P.1 variant first identified in Brazil and the L452R first seen in California.
“We need to have a really comprehensive review and discussion of this as quickly as possible because you know this new variant B.1.1.7 could cause a surge in our cases within weeks,” Osterholm said. He described the emergence of these variants as similar to a hurricane approaching on the horizon.
“I feel like I’m sitting here on a beautiful beach – the light breeze, perfectly blue skies and everybody – and I’m telling them to start to evacuate. People are saying, ‘Are you crazy?’ But I see that 450 miles south, there’s a category five hurricane,” Osterholm said. “That’s the challenge. How do you get people to take action?”
Other experts, however, argue that having a longer period of time between vaccine doses could come with the risk of being more vulnerable to the novel coronavirus and its variants.
Overall, Fauci said on Monday that getting vaccinated against Covid-19 can help prevent more coronavirus variants from emerging in the future.
“You need to get vaccinated when it becomes available as quickly and as expeditiously as possible,” Fauci said during Monday’s White House briefing, adding that viruses cannot mutate if they don’t replicate.
White House concerned about providers holding back doses
The Biden administration expressed concern on Monday that health care providers could essentially be hoarding Covid-19 vaccine doses for second shots that could be administered for initial shots.
“We believe that some health care providers are regularly holding back doses that are intended as first doses, and instead keeping them in reserve for second doses for patients,” Andy Slavitt, White House Covid-19 senior adviser, said at Monday’s virtual briefing. “We want to be clear that we understand why health care providers have done that, but that it does not need to happen, and should not happen.”
As of Monday, nearly 50 million doses of coronavirus vaccine have been distributed across the United States and about 32 million doses have been administered so far, according to the CDC.
CDC data show that about 26 million people have received at least one dose so far – but, among them, nearly 6 million have received their two doses.
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“On January 20, states had administered 46% of their inventory. Today, that number is 62%. We are focused on this every hour of every day,” Slavitt said on Monday.
Slavitt suggested that in some cases, patients’ appointments for a first dose are being canceled and pressed the urgency in getting first doses out as quickly as possible. He said the administration’s move last week to provide a three-week window into vaccine shipping plans was meant to allay concerns that second doses could get held up.
CNN’s Jen Christensen, Amanda Sealy, Michael Nedelman and Betsy Klein contributed to this report.