The prospect of a fourth wave of coronavirus, with new cases rising sharply in the Upper Midwest, has sparked a debate among vaccine experts over how long to wait between the first and second doses. Extending the period will quickly increase the number of people with the partial protection of a single shot, but some experts fear that it could also lead to dangerous new variants.
In the United States, two-dose vaccines are given three to four weeks apart, which is similar to what has been tested in clinical trials. But in Britain, health authorities have delayed doses by up to 12 weeks to reach more people faster. And in Canada, with some precious vaccines, a government advisory committee on Wednesday recommended that second doses be delayed even longer, up to four months.
Some health experts think the United States should follow their example. Dr. Ezekiel J. Emanuel, a co-director of the Healthcare Transformation Institute at the University of Pennsylvania, suggested that U.S. vaccines should go to people receiving their first dose for the next few weeks.
“That should be enough to suppress the fourth boom, especially in places like Michigan, like Minnesota,” he said in an interview. Dr. Emanuel and his colleagues published the proposal in an open in USA Today on Thursday.
But opponents, including health advisers from the Biden government, argue that delaying doses is a bad idea. They warn that it will leave the country vulnerable to variants – those already in circulation, as well as new ones that could develop in the bodies of partially vaccinated people who could not quickly fight an infection.
“It is a very dangerous suggestion to leave the second dose at a later time,” said Dr. Luciana Borio, the former acting chief scientist of the Food and Drug Administration, said. Dr Anthony S. Fauci, the country’s leading expert on infectious diseases, agrees. “Let’s go with what we know is the optimal level of protection,” he said.
The seeds of the debate were planted in December when clinical trial scientists gave their first look at how well the vaccines work. In the clinical trial for the Pfizer-BioNTech vaccines, for example, volunteers enjoyed robust protection against Covid-19 two weeks after the second dose. But just ten days after the first dose, researchers could see that the volunteers got sick less often than those who received the placebo.
In the same month, Britain experienced an increase in cases caused by a new, highly transmissible variant called B.1.1.7. After the British government approved two vaccines – from Pfizer-BioNTech and AstraZeneca – it decided to fight the variant by delaying the second doses of both formulations by 12 weeks.
In January, some researchers campaigned for the United States to follow Britain’s example.
“I think, before this boom, we need to get as many doses in as many people over the age of 65 as possible to reduce a serious illness and death that will occur in the coming weeks,” Michael T said. Osterholm of the University of Minnesota said on January 31 on NBC’s “Meet the Press”.
But the government took the lead, arguing that it would be unwise to go to the unknown in the midst of a pandemic. Although the clinical trials showed early protection at the first dose, no one knew how well the partial protection would last.
“If you’re talking about something that could cause real damage, you need empirical data to support it,” said Dr. Céline R. Gounder, an infectious disease specialist at Bellevue Hospital Center, said. plate. “I do not think you can make sense of this.”
But over the past few weeks, proponents of delayed doses have been able to point to increasing evidence to suggest that a first dose may provide potent protection that lasts for several weeks.
The Centers for Disease Control and Prevention reports that two weeks after a single dose of Moderna or the Pfizer BioNTech vaccine, the risk of coronavirus infection dropped by 80 percent. And researchers in Britain have found that the protection of the first dose is continuous for at least 12 weeks.
Dr. Emanuel argued that Britain’s campaign to get first doses in more people had played a role in the 95 per cent drop in cases since their peak in January. “It was pretty amazing,” said Dr. Emanuel said.
He cites data such as this as further evidence that the United States needs to extend vaccinations. He and his colleagues estimate that if the country had used a 12-week schedule since its inception, another 47 million people would have received at least one dose by 5 April.
Sarah E. Cobey, an epidemiologist and evolutionary biologist at the University of Chicago, said she believes the United States has lost a precious opportunity to save many lives with such a strategy. “We missed a window and people died,” she said.
But even now, dr. Emanuel said, it is worth postponing doses. The United States spends about three million vaccines a day, but almost half goes to people who have already had one chance. The whole country’s offer, he argued, should rather go to beginners.
If that happened, the United States would take two or three weeks to overtake Britain, according to its team. The extra protection will not only save the lives of the vaccinated, but also reduce the transmission of the virus to people who are still getting protection.
However, some scientists say it is premature to recognize the delayed vaccination schedule for the decline in Britain.
“They did a few other things, like closing down,” said Dr. Fauci said.
“I think the real test will be whether we will see a rebound in the cases that reopen the UK.” Dr. Gounder said.
Instead of experimenting with vaccination schedules, critics say it would be wiser to take basic preventative measures such as wearing masks seriously. “It is crucial that we do not just reopen to a major national party,” Dr Borio said.
She and others are also concerned about recent studies showing that a single dose of Moderna or Pfizer-BioNTech does not work as well against certain variants such as B.1.351, which was first found in South Africa.
“Relying on one dose of Moderna or Pfizer to stop variants like B.1.351 is like using a BB gun to stop a loading rhino,” said John P. Moore, a virologist at Weill Cornell Medicine, said.
Dr Moore said he was also concerned that the postponement of doses could promote the distribution of new variants that could better resist the vaccine. Because coronaviruses repeat within the bodies of some vaccines, they can get mutations that enable them to evade the antibodies generated by the vaccine.
But dr. Cobey, who is studying the evolution of viruses, said she is not worried about delayed doses giving more variants. “I would put my money on it with the opposite effect,” she said.
Last week, she and her colleagues published a commentary in Nature Reviews Immunology in defense of the dose delay. If more people are vaccinated – even with moderately less protection – it could hamper the spread of the virus in a community more than fewer people protect, they said. And the decline would not only mean more lives were saved. Variants also have a lower chance of showing up and spreading.
“There are fewer infected people in which variants can occur,” she said.
Dr. Adam S. Lauring, a virologist at the University of Michigan who was not involved in the comments, said he feels that dr. Cobey and her colleagues made a compelling case. “The arguments in that piece really resonate with me,” he said.
Although it seems unlikely that the United States of America will change, its neighbor to the north has adopted a delayed strategy to deal with a thriving pandemic and a shortage of vaccines.
Dr. Catherine Hankins, a public health specialist at McGill University in Montreal and a member of the Covid-19 Immunity Task of Canada, endorsed the decision, based on the emerging evidence across single doses. And she said she believes other countries that have it worse should consider it as well.
“I would advocate worldwide that countries take a closer look at Canada’s strategy and think seriously about it,” he said. Haskins said.