Why the launch of the Covid vaccine is not enough to contain infections

The coronavirus pandemic in the United States has spread almost uncontrollably for so long that millions of vaccinations will not be able to prevent the spread of the disease, unless people continue to wear masks and maintain measures of social distance until mid-summer or later. , according to a new model by scientists at Columbia University.

The arrival of highly effective vaccines in December raised hopes that they would eventually slow or prevent the spread of the disease to the rest of the population. But vaccines alone are not enough, the model shows. And if precautions like working remotely, limiting travel and wearing masks are relaxed too soon, it could mean millions more infections and thousands of deaths.

There is no doubt that vaccination protects the recipient. Still, several infectious disease researchers contacted by The New York Times warned that it would be months before enough people in the United States received the injections to allow a normal life to begin again.

Only then will the number of people with immunity – those who contracted the disease and recover, plus those who were vaccinated – be large enough to take the wind out of the pandemic, said Jeffrey Shaman, a Columbia epidemiologist who shared his team’s calculations of modeling.

Dr. Shaman estimates that more than 105 million people have already been infected in the United States, well above the number of reported cases. And its projections show that millions of other infections are yet to come, with the launch of the vaccine.

Social detachment, masking and other measures are expected to remain in effect until the end of July, “and that can be optimistic,” said Dr. Shaman. Otherwise, another resurgence of the virus is possible.

“There are people who are going to want to relax the controls that we have in place,” said Dr. Shaman. “If we start thinking, ‘We have a vaccine, there is a light at the end of the tunnel, we can stop in a few months’ – this is too soon.”

The next few months are crucial in the race to reduce new infections and deaths, since, in the end, there will be fewer people for the virus to infect as the pandemic advances.

The lifting of restrictions in early February, after most health professionals and nursing home residents are due to be vaccinated, would still mean far more infections in the long run than keeping the restrictions in place until mid-March, for example.

Even with current precautions, some areas of the country have let the pandemic spread so uncontrollably that it is too late for the vaccine to have a major impact, Shaman said. His group estimates that 60% of North Dakota’s population has already been infected. Vaccines will help, but the pandemic will end itself, as fewer and fewer people are available to infect, he said.

On the other hand, in Vermont, with an infection rate of approximately 10%, the vaccine could protect almost the entire population if it were implanted quickly enough, said Shaman. California is wavering somewhere in between, as new outbreaks occur.

The model takes into account factors such as speed and order of distribution of the vaccine, effectiveness of the vaccine after one and two doses, measures of social distance in effect and the transmissibility of the virus. He assumes that groups such as healthcare professionals and older adults will be prioritized according to CDC guidelines, and vaccination will continue at an accelerated rate of up to five million doses per week.

The group considered scenarios in which the current social distance measures were relaxed before or after the vaccine was implanted and what could happen if they were strengthened. The research was funded by Pfizer, one of the vaccine manufacturers, as well as the National Science Foundation and the Morris-Singer Foundation.

Of the scenarios that the researchers examined, those in which restrictions were enforced and then maintained until a large part of the population could receive the vaccine resulted in some of the lowest total infections.

Other researchers said they agreed with Dr. Shaman’s general conclusions, although the model involves a series of approximations and has not yet been published or formally reviewed.

The discovery “passes the intestinal exam,” said Trevor Bedford, a geneticist at the Fred Hutchinson Cancer Research Center and the University of Washington. He said the timing of the vaccine’s release is an unknown quantity that could change the conclusions. The Biden government said it plans to speed up distribution, but those claims have yet to be tested.

Dr. Bedford also warned that a new variant of the virus that has recently emerged from the United Kingdom and is believed to be more transmissible than others circulating in the United States “may cause more of a spring wave than what was modeled here” .

Lauren Ancel Meyers, professor of biology and statistics at the University of Texas at Austin, said Dr. Shaman’s reasoning “everything makes sense intuitively.” Dr. Meyers said she agreed that uncontrolled outbreaks in many places in 2020 reduced the benefits of a vaccine.

“Unfortunately, we let this virus spread widely and we are launching the vaccination campaign at the height of the threat,” said Meyers. “The more the virus spreads before the vaccine reaches people, the less deaths we can prevent with the vaccine.”

Dr. Meyers added, however, that mortality figures could drop earlier than infections with the right vaccination strategy, perhaps allowing some parts of the country to open up more quickly than expected. That depends on highly exposed frontline workers and those most at risk of death being vaccinated quickly, she said.

“We can get to the point where, while the virus is still spreading, it is less deadly at the population level and lawmakers feel comfortable relaxing some of the measures we now have in place to protect our health systems and save lives” . Dr. Meyers said.

In general, the findings are probably unwelcome news for millions of people who would like to return to normal life, from a blameless night at a restaurant to talking about football results when leaving school, as soon as possible .

Lawmakers who will have to establish and sometimes impose these restrictions in 2021 are already aware of the long road ahead, Mayor Seattle Jenny A. Durkan said in an interview.

“I think modeling is absolutely reliable,” said Durkan, who received praise for incorporating science into his own political decisions. The mayor said she was preparing Seattle to continue measures of social distance “at least during the summer and probably in the fall”.

“It is human nature to have hope,” said Durkan. “I think people thought that if there was a vaccine it would be safe to reap again, and it isn’t.”

Vaccination of people provides collective protection because the virus spreads by jumping from person to person. If the virus finds someone who cannot catch the disease, it eliminates a path to infect another person.

To put it simply, in his team’s models, Dr. Shaman assumed that neither those who recovered from the disease nor those who received vaccines could develop or pass it on again. He considered the vaccine’s effectiveness to be 95 percent after the two standard doses for vaccines available now.

All models incorporate certain approximations, and Dr. Bruce Y. Lee, professor of health policy and management at City University of New York, said that scientists would be cautious when using the new calculations to determine precisely when the disease is likely to decrease . Dr. Lee said that his own model determined that the virus could fall to much lower levels in July.

This condition, sometimes referred to as “herd immunity”, does not mean that the disease has been eradicated, said Dr. Lee. “Reaching the herd immunity limit means that there are additional protective effects of people around you being immune to something ”Said Dr. Lee.

Susceptible people can still contract the disease once collective immunity is achieved, said David Engelthaler, who heads the infectious disease branch of the Translational Genomics Research Institute in Arizona. The number of cases, however, is no longer growing exponentially and may remain relatively constant, he said.

“You will not end this by achieving collective immunity; clusters and peaks continue to occur, ”said Dr. Engelthaler.

Still, he said, growth will inevitably slow and stop – in his opinion, just before what some other researchers are projecting. He said the combination of vaccine immunity and infection could begin to control the pandemic in late spring or early summer.

“Then we can start thinking about normal civilization again,” said Engelthaler.