Public Health England (PHE) has released more information on the so-called Indian variant of coronavirus, technically known as B.1.617.2.
Let’s take a look at what we know.
More transmissible, more severe?
Drawing on “multiple analyses”, the PHE researchers say it is “highly likely” that this version of the virus – now dubbed the Delta variant – spreads more easily than its predecessor, the Kent or Alpha variant. The evidence they have for this is ranked “high confidence”.
The report also says that “early evidence from England and Scotland suggests there may be an increased risk of hospitalisation” – in other words, that the Delta variant causes worse disease.
But Ian Jones, professor of virology at the University of Reading, says the suggestion of increased severity “needs to be taken with a big dose of salt”. He points out that “the same was initially suggested for the Kent variant but was later shown not to be true”.
Paul Hunter, professor of medicine at the University of Kent, is also hesitant. “I think we need to be a little cautious about assuming that the Delta (Indian) variant is intrinsically more virulent than the Alpha (Kent) variant”, he says. He notes that it’s not clear from the PHE document whether “the relative increase in risk of hospitalisation was similar in people who have had no, one or two doses of vaccine”.
With the information available it is, he says, “too early to say for certain whether the Delta variant does indeed cause more severe disease needing hospitalisation or not”.
What about vaccines?
Vaccine efficacy is a sliding scale, so the question isn’t “does a vaccine work or not?” but rather: “what proportion of infections, serious disease, or deaths does the jab prevent?”
So far, both the AstraZeneca and Pfizer jabs have scored well on all three counts against the Kent variant.
But according to PHE’s latest assessment, a single dose of either vaccine is about 15-20 per cent less effective at protecting against “symptomatic infection” from the Delta variant than against the Alpha version.
On 22 May, PHE scientists spelled out the specifics: three weeks after the first dose, both the Pfizer and AstraZeneca jabs were 33 per cent effective against symptomatic disease from the Indian variant, versus 50 per cent against the Kent variant.
But Professor Jones notes that recent data from the 4 million-person Zoe study, and the current case reductions in India, “suggests [the Delta variant] is also controlled by vaccination”.
And symptomatic infection is only one part of the calculation. In practice, what we’re most interested in is how effective the jabs are at stopping severe disease and death. Those are the things that are most important when we’re talking about overwhelming the NHS and needing lockdowns.
PHE says there is currently “no data” on the vaccines’ ability to prevent severe illness from the Indian variant.
Professor Hunter says: “What we can be confident about with available data is that if you have had one or preferably two doses of vaccine you are rather less likely to catch either Alpha or Delta variants and even if you do become infected you are less likely to need hospital admission.”
According to new analysis by Public Health England, it’s very likely that the Indian or Delta variant spreads more easily than the Kent (Alpha) variant.
There is some limited evidence that it may also cause more severe disease, though experts warn against jumping to conclusions on this point.
The first doses of the Pfizer and AstraZeneca vaccines appear to be 15-20 per cent less effective against the Indian variant than the Kent version when it comes to preventing symptomatic infection.
But again, we’re still waiting for data on the key question of how much the jabs protect against severe disease and death from the Delta variant. In any case, it looks like getting a second dose is important.
Responding to the latest analysis, Professor Ian Jones says: “This is not a sudden change for the worse; rather it illustrates that the immune status of the population in the affected areas is key and that this needs to be as high as can be realistically achieved.”