Why the deployment of the Covid vaccine is not enough to curb infections

The coronavirus pandemic in the United States has raged almost uncontrollably for so long that millions of vaccinations will not be able to stop the spread of the disease unless people continue to wear masks and maintain social distancing measures 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 stop 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, restricting travel and wearing masks are relaxed too soon, it could mean millions of infections and thousands more deaths.

There is no doubt that getting the vaccine protects the recipient. Yet 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 vaccines to allow normal life to resume.

Only then will the number of people who are immune – those who have had the disease and recovered, plus those who have been vaccinated – will be large enough to cut the wind from the pandemic, said Jeffrey Shaman, a epidemiologist at Columbia who shared his team modeling calculations.

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

Social distancing, masking and the like are expected to stay in place until the end of July, “and that can be optimistic,” Dr Shaman said. Otherwise, another resurgence of the virus is possible.

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

The coming months will be crucial in the race to reduce new infections and deaths, as there will ultimately be fewer people the virus infect as the pandemic continues.

Lifting restrictions in early February, after most healthcare workers and nursing home residents are vaccinated, would mean far more infections in the long run than keeping the restrictions in place until mid-March , for example.

Even with current precautions, parts of the country have allowed the pandemic to rage so uncontrollably that it is too late for the vaccine to have a major impact, Dr Shaman said. His group estimates that 60% of the population of North Dakota has already been infected. Vaccines will help, but the pandemic is mostly draining itself off as fewer and fewer people are available to infect, he said.

On the flip side, in Vermont, with an infection rate of around 10%, the vaccine could protect almost any population if deployed quickly enough, Dr Shaman said. California is teetering somewhere in between as new outbreaks occur.

The model takes into account factors such as the speed and order of vaccine distribution, vaccine effectiveness after one and two doses, current social distancing measures, and the transmissibility of the virus. It assumes that groups like healthcare workers and the elderly will be prioritized according to CDC guidelines, and vaccination will continue at a rate of up to five million doses per week.

The group looked at scenarios in which current social distancing measures were relaxed earlier or later in the vaccine rollout, and what might happen if they were strengthened. The research was funded by Pfizer, one of the vaccine makers, as well as the National Science Foundation and the Morris-Singer Foundation.

Of the scenarios the researchers looked at, those in which restrictions were tightened and then kept in place until a large portion of the population could receive the vaccine resulted in some of the rarest total infections.

Other researchers have said they agree with Dr Shaman’s general conclusions, although the model involves a number of approximations and has yet to be published or subjected to formal review.

The discovery “passes the gut test,” said Trevor Bedford, a geneticist at the Fred Hutchinson Cancer Research Center and the University of Washington. He said the pace of the vaccine rollout was an unknown that could change the findings. The Biden administration has said it intends to speed up distribution, but those claims have yet to be tested.

Dr Bedford also warned that a new variant of the virus which recently emerged from the UK and believed to be more transmissible than others circulating in the US “could 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 that Dr Shaman’s reasoning “everything makes intuitive sense”. Dr Meyers said she agreed that the uncontrolled outbreaks in many places in 2020 had reduced the benefits of a vaccine.

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

Dr Meyers added, however, that death numbers could drop sooner than infections with the right vaccination strategy, possibly allowing parts of the country to open up faster than expected. It depends on frontline workers at high risk and those most at risk of dying to get the vaccine quickly, she said.

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

Overall, the results are likely bad news for millions of people who would love to return to normal life, from a guilt-free night out at a restaurant to a discussion of football scores after school, as soon as possible.

Policymakers who will need to establish and sometimes enforce these restrictions in 2021 are already aware of the long term ahead, Seattle Mayor Jenny A. Durkan said in an interview.

“I think the modeling is absolutely believable,” said Ms. Durkan, who has received praise for incorporating science into her own policy decisions. The mayor said she was preparing Seattle to continue social distancing measures “at least through the summer and probably into the fall.”

“It’s just human nature to hope,” Ms. Durkan said. “I think people thought if there was a vaccine it would be safe to come together again, and it isn’t.

Vaccinating people offers collective protection because the virus is spread by jumping from person to person. If the virus encounters someone who cannot catch the disease, that rules out a path for infecting someone else.

For simplicity, in his team’s models, Dr Shaman assumed that neither those who recovered from the disease nor those who were vaccinated could develop or transmit it again. He estimated the vaccine’s efficacy to be 95% after the two standard doses for currently available vaccines.

All models incorporate some approximation, and Dr Bruce Y. Lee, professor of health policy and management at New York City University, said scientists would be cautious using the new calculations to determine precisely when the disease is likely to go away. . Dr Lee said his own modeling determined the virus could drop to much lower levels by July.

This condition, sometimes called “herd immunity,” does not mean the disease has been eradicated, Dr Lee said. “Reaching the collective immunity threshold means that the people around you are immune to something,” Dr Lee said.

Vulnerable people can still contract the disease once herd immunity is achieved, said David Engelthaler, who heads the infectious disease arm of the Institute for Translational Genomics Research in Arizona. The number of cases, however, is no longer increasing exponentially and can remain relatively constant, he said.

“You’re not going to destroy this thing by getting collective immunity; clusters and peaks continue to occur, ”said Dr. Engelthaler.

Still, he said, growth will inevitably slow down and stop – in his opinion, a little sooner than some other researchers predict. He said the combination of vaccine immunity and infection could start to curb the pandemic in late spring or early summer.

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