Continued mutation of the coronavirus destroyed the hope for herd immunity

Irja Lutsar. Photo: Gert Tali

Irja Lutsar, Professor of virology and head of the Science Council, said in the Postimees direct broadcast that the effect of vaccines will weaken over time in case of Covid-19 infections of low and medium severity. “The weakening occurs steadily every month rather than happening suddenly on the sixth or fourth month,” she explained.

Lutsar said that vaccines protect against all strains of the coronavirus but it is also clear that the vaccines are not ideal. “The effect of vaccines is slowly receding,” she admitted.

The professor said that the vaccines were brought to the market after only two months of observation of the vaccinated test subjects, which resulted in the high efficiency percentage. “But only now we are beginning to receive data from real life which show that the initial high efficiency – over 90 percent – is beginning to decline,” Lutsar said.

This primarily concerns infections of low or medium severity. “Curiously enough, the vaccines are still highly efficient in the prevention of severe infections (cases when people are hospitalized), i.e. their efficiency is above 90 percent,” the scientist said.

The virologist explained that according to the logic of mutation of viruses, every new strain must be stronger and of higher vitality than the previous one. “Otherwise it simply would not be capable of taking over the place of the previous strain. The Delta strain drove out the Alpha strain and the Alpha strain overcame the earlier ones,” she said.

According to the professor, the spreading potential of the Delta strain is approximately 1.5 times stronger than the previous one. “It is multiplying faster and its concentration in the nasopharynx is higher, therefore there are more carriers to be transferred.”

On the other hand, Lutsar is convinced that the existing immunization measures work on the delta strain and this mutation does not pose particular threat to the protection offered by vaccines. “The efficiency of vaccines began to decline even before the Delta strain was massively spreading. But it is correct that the efficiency of vaccines against the Delta strain is approximately ten percent lower. While the efficiency against the Wuhan strain was 91–92 percent, it is more like 81–82 percent against the Delta strain,” she said.

It is also clear by now that even the vaccinated people can transfer the virus. Critics of the corona pass therefore question the need for checking the vaccination certificates. But the head of the Science Council considers the immunization passports necessary.

“Once the coronavirus enters the nasopharynx of an unvaccinated person, nothing opposes it there. The virus will enter the cells and will multiply there,” Lutsar said, adding that in the organism of a vaccinated person, antibodies will attack the virus and will destroy it.

The professor also assured that a vaccinated person has a four times lower likelihood to be infected than a person who has not had the shots. “Even if the individual gets infected, the likelihood of being hospitalized is halved,” Lutsar added. She summed it up in figures: the likelihood of a vaccinated person being hospitalized is ten times lower than that of an unvaccinated person.

While the researchers were still hopeful in spring about the emergence of herd immunity, the views have changed by now. “We know that the coronavirus is mutating very rapidly and I doubt whether the Delta strain will be the last. There will certainly be new mutations and it is likely that herd immunity cannot be achieved against Covid-19;” Lutsar admitted.

On the other hand, the virologist said that efficient individual immunity can be achieved and that will again depend on vaccination. “Instead of the herd immunity, every individual can achieve immunity through vaccination or getting infected and recovering,” the professor said.