Epidemiologist – on the spread of delta coronavirus in Lithuania: poses a double threat

How is it different from other strains of coronavirus, whether it can cause more serious consequences, unusual complications and whether it is resistant to the vaccine, Dr. Gytis Dudas, a genomic epidemiologist, told Delfi rytas.

– It is already known that the Indian variety virus is spreading faster. What other differences does this strain have compared to the primary coronavirus?

– The spread of the delta variety, as the World Health Organization calls it, is in fact more efficient than the alpha variety, the so-called British variety. This causes additional inconvenience.

Another thing is that this strain is more likely to be re-infected when it has been reinfected, infected with other strains that do not have some of the mutations that this strain has, or vaccinated with currently registered vaccines.

Thus, this threat is twofold compared to previous strains, such as the alpha strain, which, although it may have spread more effectively, the available vaccines act against it, or the beta strain, the so-called South African strain, which we know may have more success in infecting sick or vaccinated people, but so far there is no unequivocal evidence that it spreads more effectively.

The delta strain, the so-called Indian strain, has the double problem that they both spread significantly more efficiently than the alpha strain and, at the same time, can infect humans more successfully. We are also gradually getting evidence that people are much more likely to end up in hospitals with this stress, which would automatically increase both hospital workload and mortality.

– What evils can this delta variety cause?

– Hospitals will be even more burdened if this strain reaches the unvaccinated part of the population and mortality will be higher.

– Is this variety now dominant in Europe?

– Not for now. This strain is so far predominant in the United Kingdom (UK), where things seemed to be going well as a higher proportion of the population has been vaccinated. With the advent of this variety, a small wave began there again.

We can also very easily see that more than half of the cases in Russia since mid-May are caused by this particular variety. Russian President Vladimir Putin has already announced that vaccination will be mandatory for all public sector workers, although two weeks ago it was said that it would be a major violation of human rights and the like.

So the problem really is. In Lithuania, if we continue to vaccinate successfully, we can avoid such a major wave. Because after both doses of the vaccine, both AstraZeneca and Pfizer are significantly less likely to be hospitalized. Protection with both doses of Pfizer against delta hospitalization is 96%. – this is a significant reduction in risk.

– What about vaccines from other manufacturers?

– So far, only studies have been published on the AstraZeneca and Pfizer vaccines. When vaccinated with AstraZeneca, protection after a full vaccination regimen is not bad either. The problem is, with just one dose, there is that protection, but if I’m not mistaken, AstraZeneca is only around 30 percent and Pfizer is around 50 percent. The interval between two AstraZeneca doses is quite long, so even in the UK there is probably still a large enough part of the population vaccinated with a single dose.

– If this strain is able to avoid the immune response that may have developed after vaccination or after relapse, there is a risk not only of infection but also of serious complications or even death. Do you still save against the worst-case vaccine if you’ve been vaccinated with both doses?

– Absolutely! Both doses of the vaccine reduce that risk as much as possible. Both doses of Pfizer provide more than 80% protection against symptomatic disease. And, as I mentioned, the protection against hospitalization is 96%, which is a significant figure. So it all depends on how voluntarily people get vaccinated.

– What other actions can be taken to prevent the spread of this variety?

– Something extra, in addition to the voluntary use of masks, extra absence in closed, non-ventilated spaces, as is not the case. You just need to get vaccinated and be careful.

– The coronavirus that caused the global pandemic has been spreading around the world for just over a year, but has mutated more than once. Is this virus mutating differently from others? Does it mutate more often?

– One thing that should be made clear to the public is that everything that exists and reproduces undergoes mutations.

The number of mutations there are does not necessarily tell you what the threat is. More importantly, what mutations occur in the body. Let’s say the British alpha strain had many mutations, but we know of only a few that made it so threatening. The same goes for the delta strain: there are not many of these mutations, but we see that their effect is incomparably stronger.

It just doesn’t make sense to compare viruses by the number of their mutations or how quickly they mutate.

– So this delta variety is neither the first nor the last?

– Absolutely! The more the virus circulates in humans, the more mutations we will see. It is difficult to predict exactly what mutations will happen, what their effects will be; in any case, it is evolution.

One thing we could try to do is make vaccines available to people around the world. Then we can reduce the spread of the virus. And the less that virus is, the less chance it will have of mutating.

– Now the summer, the holiday season and Lithuanians are also planning trips abroad. What advice would you give to compatriots traveling abroad so that they don’t carry an unexpected variety?

– One thing that would help significantly is the requirement of a negative test before returning. This automatically improves the situation.

One of the most important things would be to make sure that people are properly insulated when they return. We have seen it more than once with a sequencing project when we discovered different varieties that we would not want to have.

We saw the introduction of B. 1620, the so-called Puntukas. We had two entrances and only one of them was extended because the first one we encountered was a traveler who returned, neatly isolated. The chain of infections did not start from that person.

We saw exactly the same with the first gamma, the so-called Brazilian variety, when a traveler arrived and infected it. A sample from that person accidentally fell into our sequencing sample, but the traveler did not spread that infection in Lithuania.