A Covid-19 lesson for the US from three countries with rapid rollout of vaccinations

Epidemiologists say there is a real risk of a so-called exit wave of new infections as countries drop their guard as shots increase as vaccines do not provide 100% protection against contracting Covid-19. New variants of coronavirus that can bypass the immunity from vaccination or previous infection increase the risk of another wave.

If restrictions are relaxed too soon, the virus will seize its opportunity, scientists say.

“We are in a race of sorts between vaccination and virus,” said Graham Medley, professor of infectious disease modeling at the London School of Hygiene and Tropical Medicine.

Still, even with a new wave of infections, scientists are optimistic that a broad vaccination coverage should provide significant protection against serious illness and death. Data from all three countries shows that high-risk groups that received vaccination priority remain largely disease-free.

According to ministries of health and data collected by the University of Oxford’s Our World in Data project, Israel has so far given at least one dose of vaccine to 62% of its population, the UK to 48% of its population and Chile to 40%.

The US has given 39% of the population an injection or more and the 27 members of the European Union together vaccinated only 18% of theirs.

Israel offers a lesson in what happens when vaccination outstrips the virus. The country suffered an average of more than 8,000 new infections per day at the height of its last great wave in mid-January. New cases are now in the low hundreds. Some Israeli hospitals, including the country’s largest Sheba Medical Center, have started closing their Covid-19 treatment units.

Residents cram into bar restaurants when the Israeli economy reopened in March and students returned to classrooms, sparking concern that another wave was imminent.

Instead, cases continued to decline, suggesting that widespread immunity to vaccination or previous infection is controlling the spread of the virus.

“A lot of people, including us, said it is possible we could get another wave in March,” said Eren Segal, a computational biologist at the Weizmann Institute in central Israel and a member of a government civil advisory committee on coronavirus problems. “We are very happy that it has not happened so far.”

Prof. Segal said there will be an even smaller chance of a resurgence by the summer as Israel is expected to inoculate many of its 12 to 15-year-olds by then, further reducing the size of the susceptible population. An extensive testing program aims to control the virus in younger children. Researchers now say they don’t expect spikes in infections anymore unless a vaccine-resilient variety enters the country.

Chile’s vaccination campaign has been a bright spot in Latin America as neighbors struggle to take their own photos as they are battered by a second wave of infections.

But the country is grappling with a wave of new infections that forced President Sebastián Piñera’s government to implement another lockdown, close the borders and postpone the elections scheduled for this month. New cases of coronavirus soared above 9,000 per day this month, the highest daily total, allowing hospitals with an influx of younger patients to thrive.

Health experts say the increase in infections highlights the risk of relaxing social disabilities before enough people are vaccinated to prevent the virus from spreading, and the threat of variants such as P.1, first identified in Brazil.

Some epidemiologists say Chile was too fast to celebrate its rapid rollout of vaccinations. When officials relaxed restrictions, residents showed their vigilance to measures such as wearing a mask, washing hands and social distancing, believing the pandemic would soon be over, said Claudia Cortés, an infectious disease expert at the University. from Chile.

“They gave the wrong message,” she said. “It was very confusing for the general population.”

Chile also relies heavily on the Chinese Sinovac vaccine, which the Chilean government said last week was only 16% effective at reducing the risk of infection after one injection and 67% effective two weeks after the second dose.

Officials and doctors say the vaccines are starting to show results. As the number of cases increases among people under the age of 60, infections are beginning to decline for high-risk elderly people, whose deaths have leveled off, according to government data. The two-dose regimen is 80% effective in preventing death from Covid-19, the government said.

“There is now a clear trend that we can see with the separation of the curves between people over 70 and younger people who are just starting to vaccinate,” said Miguel O’Ryan, public health expert at the University of Chile. .

British officials, grappling with vaccine supply issues as they plot a route out of a strict lockdown needed to control the infectious B.1.1.7 variant first discovered in England, consider Chili’s experience as a cautionary tale. The country has suffered the highest death toll in Europe, and scientists and public health experts advising the government are pushing for a slow and gradual lifting of restrictions to ensure vaccinations continue to outpace the virus.

Disease models advised by the British government have analyzed the possible course of the pandemic in the coming year if restrictions on the economy and daily life are relaxed, in line with Prime Minister Boris Johnson’s four-step plan, which cannot be locked.

Their work highlights the risk of an exit wave, with one model from Imperial College London epidemiologists suggesting that the UK could have an additional five million cases by June 2022 if controls are relaxed as planned. That’s more than the four million known cases already recorded, although gaps in testing at the start of the pandemic mean that the actual number of infections is likely to be much higher.

Vaccination means that hospitalizations and deaths from Covid-19 are likely to be much lower than at previous peaks of the pandemic, according to the models. But they are still substantial, with Imperial’s model, for example, pointing to as many as 15,700 deaths through June 2022. So far, there have been 150,000 deaths in the UK with Covid-19 listed on the death certificate.

A panel of scientists advising the government said in a report that the magnitude of an exit wave will be hugely sensitive to things like the speed and rate of vaccine intake, any delivery problems, and the still uncertain role that warm weather and summer behavior play. in limiting the spread of the virus.

Another critical factor is how effectively the vaccines counteract transmission, beyond just preventing infection or serious illness.

A vaccine that is highly effective at stopping transmission would likely mean far fewer cases and very few deaths, said Prof. Medley, who sits on the advisory panel.

Scientists are still collecting data on the effect of vaccines on the spread of the virus. Studies from Israel and the UK suggest the vaccine developed by Pfizer Inc.

and BioNTech SE is very effective in preventing further transmission.

Write to Jason Douglas at [email protected] and Ryan Dube at [email protected]