Amid good news about rising Covid-19 vaccination rates and starting to decline in infections, Boris Johnson shocked listeners at his press briefing on Friday with an unexpected announcement that the new, more contagious variant of the coronavirus is also more deadly.
After scientists first recognized in mid-December that the B.1.1.7 variant outperformed previous versions of the virus with its rapid spread from south-eastern England and the UK, they said that it was about 50% more transmissible but seemed not to cause more severe symptoms.
How strong is the new evidence that the variant kills a greater proportion of people than it infects?
The Government’s Advisory Group on New and Emerging Respiratory Virus Threats (Nervtag) reviewed studies by three academic teams and Public Health England, comparing death rates between people known to have been infected with B.1.1.7 and those with older forms of coronavirus. As far as possible, they corrected other factors that could influence mortality, such as age, location and ethnicity.
All studies showed some increase in lethality, although uncertainties in the data resulted in a wide range of estimates. Collecting their results, scientists at Nervtag produced a model showing that a person infected with B.1.1.7 has a 30-40% more chance of dying than a person with a different variant.
Patrick Vallance, the government’s chief scientist, quoted the estimate during the Downing Street briefing. “I want to point out that there is a lot of uncertainty around these numbers,” he said, “and we need more work to get a clear picture, but it is obviously worrying that this results in an increase in mortality. ”
Most scientists who commented on Nervtag’s assessment believe that the available evidence supports the general conclusion of higher mortality, although the magnitude of the effect needs to be clarified. The outer bounds of estimates in studies reviewed by Nervtag ranged from an additional risk of 7 percent to 271 percent of B.1.1.7.
If the discovery that the new variant is more deadly, what difference will it make for individuals?
Consider the central estimate that B.1.1.7 has a 30-40% higher probability of death. The impact of this relative risk on an individual will critically depend on their absolute risk – determined first and foremost by age, then by underlying health and other factors. Evidence reviewed by Nervtag suggests that the variant increases case fatality rates consistently across all age groups.
Sir Patrick took the example of men in their sixties. The average risk was that about 10 in 1,000 people would die from infection with the old virus; with the new variant, 13 or 14 would die.
For healthy children and young adults, who are extremely unlikely to die from Covid, the additional lethality of B.1.1.7 would have a minimal effect on their absolute risk. Conversely, it would have a significant impact on people over 80 who are already at high risk.
It should be remembered that death rates are already considerably lower than they were during the first wave of the pandemic in the spring, as health workers learned how to best treat patients with Covid-19, when administering the dexamethasone steroid to those who are seriously ill. . Even if the new variant increases the risk of death by 35%, it would still be lower than that of a person with the original form of the virus in March.
What would be the impact of a more lethal variant on overburdened health services?
The increased transmissibility of B.1.1.7 has already elevated the disease to a very stressful level hospitals, particularly in London and in the south-east of England where it is responsible for the majority of Covid-19 cases.
Nervtag’s analysis suggests that the new variant does not increase death rates in people who are already hospitalized with Covid-19, said Rowland Kao, professor of epidemiology at the University of Edinburgh.
“The increase in the number of deaths is the result of more severely infected and hospitalized people, rather than more hospitalizations resulting in death,” he said. “As such, it would appear that the new variant is also responsible for the increased and surprisingly high load in hospitals, especially around London.
Will the immunization schedule need to change?
A more lethal variant is unlikely to change the balance of the heated medical debate over how to deploy Covid-19 vaccines – and in particular the government’s decision to inoculate as many people as possible with a first dose, even so they have to wait as long as 12 weeks for the second jab.
The British Medical Association has called for the wait for a second dose to be reduced to a maximum of six weeks for the BioNTech / Pfizer vaccine. But supporters of the current policy say a more virulent variant makes it even more important to vaccinate vulnerable people as quickly as possible.
Yvonne Doyle, medical director of Public Health England, told BBC Radio on Saturday that the current strategy of “reducing transmission” would reduce the number of deaths and reduce the risk of the emergence of more dangerous variants of the virus. “The more people there are protected against this virus, the less opportunities there are to gain the upper hand,” she said.