Sat, October 23, 2021

in-focus

U.K. experiment to combat covid variant


LONDON - Faced with soaring hospitalizations and deaths, Britain is launching a daring campaign to combat a ferociously infectious variant of the coronavirus by spacing the first and second doses of approved vaccines out over months instead of weeks.

The full vaccine deployment plan will be published by the government Monday, but the difficult decision to alter the recommended vaccination schedules will apply to the entire population, including the elderly and health-care workers.

Without enough doses immediately available, public health officials are betting that crucial second injections of two approved vaccines can be pushed back from their recommended waiting intervals - 21 days for Pfizer and 28 days for AstraZeneca - to 84 days for both.

The government's science advisers say there is little choice, given the explosion in cases, even as they acknowledge that delaying the second dose involves risk. Clinical trials did not test the efficacy of the vaccines when administered on such an elongated schedule.

When Britain first proposed a three-month wait between doses, scientists in the United States, Europe and at the World Health Organization sounded dubious.

The Food and Drug Administration earlier this week said it would be "premature" and "not rooted solidly in the available evidence" to change the way the two authorized vaccines are administered.

On Friday, a spokesman for President-elect Joe Biden said the incoming administration will release nearly every available dose of vaccine in the United States after Biden takes office Jan. 20 to get supplies quickly out to the states. The move marks a switch from the current policy of holding back half to ensure second doses are available to those who have received a first dose.

The spokesman did not say the plan, to be spelled out in detail next week, will entail delays in people getting their second doses.

Limited data suggests a single shot of the Pfizer or AstraZeneca vaccines affords some protection against disease. For example, the first jab of the Pfizer vaccine was 52% effective in the three-week interval before people received the booster shot. Similar results were described for the Moderna vaccine, which British regulators approved for emergency use Friday.

But it is not known how long the protection lasts.

Britain's health secretary, Matt Hancock, said earlier that a 12-week interval between doses will mean individuals might be less protected from the virus, but society overall will see more people vaccinated more quickly. That is the essential trade-off.

Hancock stressed that a single dose should protect most from the severe symptoms of covid-19 that send patients to overstretched hospitals and ICUs.

British scientists have largely supported the plan, acknowledging that the country faces a race between vaccines and the virus.

"It is safest and most cautious to use the vaccines in the exact conditions reflecting the trials," said Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine. "However, this will never be possible in the real world, and the question is how much moving outside the exact conditions is acceptable."

On Friday, the WHO offered interim guidance that partially backed Britain's approach, saying the period between the first and second doses of the Pfizer vaccine can be up to six weeks instead of the three weeks recommended.

WHO experts noted many countries are facing a crisis.

"Countries experiencing exceptional epidemiological circumstances may consider delaying for a short period the administration of the second dose as a pragmatic approach to maximizing the number of individuals benefiting from a first dose while vaccine supply continues to increase," its guidance said.

Britain is being hammered by a third wave of covid-19, driven by a highly transmissible variant of the coronavirus. The country is under another national lockdown.

London Mayor Sadiq Khan on Friday said that the new variant is raging "out of control" and that hospitals are in danger of being overwhelmed.

More than 1 in 20 people in some parts of the capital city are infected, Khan said. In England overall, 1 in 50 are infected.

One respiratory physician wrote in the Guardian that London hospitals are rationing access to oxygen, with doctors having to decide who can be saved.

"This is a national challenge like nothing we've seen before," said Prime Minister Boris Johnson at briefing Thursday, when he announced that the British military has been given the job of coordinating the delivery of millions of doses.

Britain has so far given 1.5 million people the Pfizer vaccine, alongside the first doses of the newly approved AstraZeneca-Oxford shot, in an early rollout Johnson hailed as the most advanced in Europe. The Moderna vaccine won't be available in Britain until spring.

By mid-February, the government aims to have vaccinated the 15 million people in the top four priority groups, which include all those over 70 years old along with all residents of nursing homes, front-line medical and care workers, and those with extremely serious medical conditions. Health officials say 88 percent of covid deaths have occurred among the over-70 cohort.

Nilay Shah, head of the department of chemical engineering at Imperial College London, told The Washington Post, "The aim is just about achievable, but everything needs to go right every single day."

Shah said the new campaign will require Britain to quickly ramp up to administering 300,000 doses a day, seven days a week, over 50 days.

Britons have watched in despair in past months as the government fell short of its promises: producing record numbers of emergency ventilators but after they were needed; struggling in the early months of the pandemic to get protective gear to front-line medical workers who were donning garbage bags instead; and repeatedly promising, but never delivering, a "world-beating" cellphone app to alert users when they have had close contact with an infected person.

The prime minister, too, has been accused of delaying decisions until events overtake him. On Sunday, he promised schools would reopen Monday. On Monday, he closed them again.

By the end of next week, Johnson said, the new campaign will be underway at 1,000 sites operated by general practitioners; at 223 hospitals and 200 pharmacies; and at seven mass vaccination centers located in sports stadiums and convention halls.

Simon Stevens, chief executive of the National Health Service, the country's publicly funded health-care system, said 80,000 workers and volunteers - including doctors and nurses brought out of retirement - will be deployed.

Stevens said the NHS is also "unashamedly tapping into armed forces" to provide logistics.

Brig. Phil Prosser, who in the past was charged with getting troops and equipment onto the battlefield, said "a vaccine program of this size has not done before."

He compared the logistical challenge to "setting up a major supermarket chain in a month."

In Britain, much of the blame for the surge in cases has been ascribed to the new variant of the virus, which research suggests is at least 30% to 70% more infectious.

Jim Naismith, professor of structural biology at the University of Oxford, told science journalists, "It is not really possible to overstate how serious this new strain is."

He warned, "If we fail to reduce the spread of the new strain, then we are likely to overwhelm the NHS."

There is no evidence at this point that the mutated virus increases disease severity, nor is it anticipated that the new variant will soon affect vaccine effectiveness, though it is also true that viruses change over time and vaccines often need to be tweaked to keep up.

The Pfizer vaccine works against a key mutation found in fast-spreading coronavirus variants first discovered in the Britain and South Africa and are now spreading across the globe.

That finding bolsters many scientists' expectations that the immune response triggered by vaccines will be broad enough to counter the highly contagious mutations. The research, led by scientists at the University of Texas Medical Branch, was published Thursday but is not yet peer-reviewed.

More experiments and direct tests of both variants in the next few weeks will bring greater clarity, scientists said. British scientists will also monitor the efficacy of the new dose regime.

Published : January 09, 2021

By : The Washington Post · William Booth