Fourth Wave Probability
Where did the information about the approach of the quadruple wave come from?
The fact that the so-called fourth wave of COVID-19 in Russia is not far off is not being said by influencers, but by officials and authoritative doctors. In early September, the head of Rospotrebnadzor, Anna Popova, in an interview with the Russia 1 TV channel, said that the forecasts of a new surge for this fall are justified. She is echoed by the head of the Moscow health department Alexei Khripun. Denis Protsenko, chief physician of hospital No. 40 in Kommunarka, told E1.RU that a new rise in the incidence can be expected at the turn of September and October.
Why are experts expecting the fourth wave?
Experts associate the risk of the fourth wave with the return of people from vacations and the beginning of the school year. An increase in the number of contacts can provoke an increase in the incidence of COVID-19. Popova pointed out that usually a surge in the incidence of acute respiratory viral infections is observed in the second decade of September. That is, the forecast of Rospotrebnadzor is based on data on the epidemiology of ARVI obtained in previous years.
Can not. Seasonality can hardly be called an important factor in the spread of the SARS-CoV-2 coronavirus. A number of studies have shown that it can be influenced by temperature, the intensity of ultraviolet radiation, and humidity (1, 2, 3). However, against the background of other factors, this influence may simply be “lost”. These factors operate mainly in the fresh air, and the coronavirus is usually transmitted indoors. This, among other things, was highlighted in a commentary to The Guardian by Professor John Edmunds, a member of the UK Emergency Science Advisory Group.
Are the forecasts of specialists justified?
They are grounded. The increase in the number of contacts could indeed lead to an increase in the number of new cases of COVID-19. In 2020, the beginning of the second rise in the incidence of this infection fell on the second decade of September (Fig.).
Now in Russia, the delta variant of the coronavirus dominates. Scientists believe that its contagiousness (infectivity) is more than twice that of the ancestor strain (1, 2). A report from the US Centers for Disease Control and Prevention, leaked to the media in July, indicated that infection is as easy as the varicella-zoster virus. This speaks in favor of the possibility of a new outbreak.
Vaccination and the transferred COVID-19 significantly reduce the risk of developing a symptomatic form and a severe course of infection caused by the delta variant of the coronavirus. However, the number of protected people is not enough to prevent a possible outbreak. More than 31% of Russians are fully vaccinated against COVID-19; since the beginning of the pandemic, this infection has been detected in about 5% of the country’s population. Previously, scientists predicted that in order to create herd immunity, at least 60-70% of the population must be ill or vaccinated. In August, at a briefing by the American Society of Infectious Diseases, it was suggested that a higher threshold of at least 80% is required to protect against the delta variant.
Will the fourth wave be more deadly?
Perhaps. This depends on the characteristics of the variant that will trigger the new outbreak. Apparently, if a surge in the number of new cases of COVID-19 happens in the near future, then it will be associated with the delta option, which prevails now. Anna Popova stated that “lambda and other strains that made such a loud noise” are not common in Russia. There were only two infections in the mu-variant, which the media often wrote about in recent weeks, in Russia as of September 9.
The contagiousness of the delta variant, which we wrote about above, can lead to high morbidity. This in itself can cause a large number of deaths.
Apparently, with a delta infection, a person has a higher risk of death than with a disease caused by his predecessors. Regarding its lethality (the ratio of the number of deaths to the number of cases), the Russian media broadcast opposite opinions of experts. Larisa Popovich, director of the Institute for Health Economics at the Higher School of Economics, told RBC that its lethality is one and a half times higher (probably compared to the original version of the virus). However, the director of the Central Research Institute of Epidemiology of Rospotrebnadzor, Alexander Gorelov, stated that he did not increase the likelihood of death and a severe course of infection.
The mortality data for the delta variant are still to be clarified. Currently, two scientific papers suggest that it may indeed be more deadly. The study, published in The Lancet, showed that in Scotland, the risk of dying from an infection caused by it was about twice that of an infection with the alpha variant (“British strain”). Vaccinated people had a 60% lower risk of death. The authors of the Canadian study, which is available as a preprint, found a similar increase in the lethality of the delta variant compared to the original variant of the coronavirus.
Thus, a new outbreak, which can be conditionally called the fourth wave of COVID-19, is possible this fall. Hypothetically, she really is capable of being more deadly. There are real prerequisites for both predictions – time of onset and mortality rate.