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Herd immunity: how it is formed and how reliable
Herd immunity is the main hope in the fight against the pandemic. But how is it formed and how reliable is it?
OPERATING PRINCIPLE
At first, the work of herd immunity for each specific pathogen depends on the mode of its transmission. COVID-19 is transmitted by airborne droplets, so the seasonal component affects herd immunity. In the cold period, there is a decline, as people are more often in crowded conditions where there is warm air – shopping centers, public transport. And in spring and summer they are dispersed – someone is resting in the country, someone is at a resort, someone is walking in the park, and the distance from a sick person is large, not enough for infection.
Secondly, the strength of herd immunity depends on the number of vaccinated individuals. In the case of coronavirus, the more people are vaccinated, the less chances of latent forms of infection occurring when one asymptomatic person can infect others. A clearly ill person is more likely to stay at home and less likely to infect others.
Third, it is also important which age strata within the group are better vaccinated. For example, in the COVID-19 epidemic, the most promoted is the vaccination of older people who are more ill and more likely to die. In terms of prevention, this is true. But in the case of herd immunity from a new coronavirus infection, the maximum immunization of young people is important. It is socially active youth that infects more vulnerable older people. Therefore, vaccination today is a manifestation of citizenship, as well as caring for those who are most difficult to bear the disease. This is our chance to get out of the pandemic as soon as possible, returning to normal life.
UNDER PROTECTION
People who have had coronavirus can also help with this, but recent data suggest that vaccination gives stronger immunity than disease. Therefore, a critical mass of vaccinated people is needed. The low rates of vaccination in Russia are due to the fact that everyone thinks: “Well, why should I get vaccinated? Let the neighbor go and I’ll wait“. And it turns out that everyone is waiting. Of course, this is also due to fashionable anti-vaccination sentiments and hysteria that the vaccine has killed someone. This has been the case at all times, and the very first smallpox vaccine a few hundred years ago followed the same path. Doctors were branded, cartoons were drawn on them, accused of all sins and deaths. But look: today smallpox has been erased from the face of the Earth, locked up in laboratories, which means that vaccination as a method ultimately works and can help us fight many infectious diseases, including COVID-19.
Vaccination makes the possibility of herd immunity for COVID-19 more achievable than for other pathogens for which vaccination does not provide a sufficiently strong or stable effect. As, for example, happens with the flu: even if we cover a large group of people with vaccination, due to the fact that the virus mutates almost every year, the herd immunity formed will not be as long, although strong. The coronavirus does not seem to mutate as quickly. And to win, it is enough for us to vaccinate about 80% of the population in order to extinguish our domestic share in the pandemic.
LIFE TIME
Since herd immunity is built from the “building blocks” of personal immunities, one would think that its duration would be equal to the duration of personal immunity from COVID-19 – today scientists say that they will have to be vaccinated every 1-2 years, but there are no exact figures yet.
In fact, herd immunity can be arbitrarily long, since all members of the group who are vaccinated do not get it on one particular day. Every day someone loses immunity, and someone gains, and someone continues to live “in the middle”, and this whole system is continuously updated due to the influx of new people, death of old people, re-vaccination of those people whose immunity has “expired” … In all likelihood, the coronavirus will remain with us forever, like the flu, and therefore we all may have to be vaccinated periodically, but our herd immunity will last indefinitely. Under ideal conditions, of course.
We do not take into account the problems with the production and supply of the vaccine, if they arise, we do not take into account the newspaper ducks that “such and such a vaccine began to kill,” and the public fear of it, as well as other things. Let’s just say that a new mutation of the virus can reduce herd immunity, which will require the creation of a new vaccine, but, fortunately, no such data has yet been obtained for the COVID-19 infection and related viruses.
HISTORICAL REFERENCE
The term “herd immunity” appeared in the middle of the 55th century, when active vaccination of the population against measles was carried out in the USA. Let us repeat that measles is a very contagious infection, and doctors who worked in that era began to notice that when the level of vaccination coverage against measles reached 80% of the population, the incidence dropped significantly, and when the mark reached 90-XNUMX%, the disease ceased to occur.
This effect is open to almost all pathogens for which vaccination is an effective control method. For example, smallpox, even more infectious than measles, was inadvertently introduced to the USSR, to Moscow in 1959 from India, although before that (in 1936) the USSR completely defeated this disease by vaccination. Among the population there were people who did not have immunity. The country’s government took unprecedented measures and extinguished the outbreak in almost a month, while fully vaccinating the entire population of Moscow and the Moscow region in 19 days.