The “Indian” variant is B16172now dominantin the UK, and there were fears its sudden surge could affect Britain’s exit from the lockdown.scientist– –including me– previously predicted that B16172 and other closely related variants could be resistant to vaccines because of the mutations they carry.
Public Health England (PHE) has therefore investigated the effectiveness of the leading vaccines against B16172. It published one form – an early work yet to be reviewed by other scientists – suggesting that the UK vaccines are still effective against B16172, just not as effective as against B117, the variant that previously prevailed in the UK.
Does that mean we don’t need to worry? Unfortunately, probably not. While the general conclusion of PHE looks correct, there are a number of things that suggest that B16172 could nonetheless cause spikes in cases in the UK, if you look closely at the results.
The effectiveness is variable
First, the dosage makes a huge difference here. After two doses, PHE actually found that the Pfizer vaccine was highly effective against B117 (93%) and only slightly less effective (88%) against B16172. The corresponding estimates for the AstraZeneca vaccine were 66% and 60%, respectively.
However, the total number of COVID-19 cases in people who received two doses of either vaccine was small, which makes these estimates somewhat uncertain. Since these results were not calculated using a lot of data, we need to be careful in giving too much credibility to these results.
However, there was a greater decrease in performance in people who received only a single dose of either vaccine (at least three weeks earlier). A single dose of either vaccine was 51% effective against B117 but only 34% effective against B16172 (the effectiveness of the AstraZeneca and Pfizer vaccines in this case being similar).
These estimates are pretty worrying considering the UK strategy still leaves 12 weeks between first and second doses. As B16172 becomes more prevalent, it may mean we are only providing 34% protection for millions of people for a few months. Widening the gap between the first and second doses (so that more people can receive the first doses in the meantime) was seen as preventing between doses 26 and 47 deaths per 100,000 people in the UK – but these results may mean that a widened gap is no longer the optimal strategy.
However, this preprint only measured symptomatic diseases and could not assess the effectiveness of the vaccines in preventing serious diseases caused by B16172. Vaccines generally appear as COVID-19 rather more effective In preventing more serious illnesses than mild or asymptomatic infections, it may still be optimal to continue the 12-week gap and give the first doses to larger numbers of people to reduce hospital stays and deaths. Whether this is actually the case should become clearer over time.
Perhaps more worrying was the finding that after two doses, the AstraZeneca vaccine was much less effective than the Pfizer vaccine against both B117 and B16172. PHE has This could be due to the fact that the second dose of the AstraZeneca vaccine is introduced later, meaning that this assessment was made before they were fully effective.
However, this has not yet been proven, and this difference between vaccines is a huge gap that needs to be closed. Given this difference, I think it is too early to argue, like PHE, that both vaccines against the B16172 variant are highly effective.
Increased infectivity is a big problem
Nor should the debate about the effectiveness of the vaccine take place in isolation from the discussions about how contagious the new variant is. There is reasonable evidence that B16172 is more contagious than previous variants – maybe 50% more.
A modest decrease in the effectiveness of the vaccine alone may be enough to improve the balance in favor of increased transmission. In combination with an increase in infectivity, transmission can increase significantly.
The strength of this combination can be seen in the rapid increase in cases of B16172 over the past few weeks. Case numbers have doubled every seven to ten days at a time when we were still in a fairly strict lockdown. This increase was masked by the dramatic decrease in B117 cases for several weeks at a time. But now that B16172 has overtaken B117 as the dominant strain, and after the May 17th relaxations, we can expect the total number of cases to grow faster.
The big question that remains to be answered is how big this new wave will be and how much pressure it will put on our hospitals. This question won’t be answered for a week or two. In fact, we don’t yet know whether B16172 makes people sicker than B117. But claims that we will likely be back to normal by summer now look a little too optimistic.