COVID-19 | Is herd immunity the goal we should pursue with vaccination?

Two years after the start of the pandemic of COVID-19, the vaccination campaigns in the various countries of the world progress at different rates. The World Health Organization (WHO) set the goal of reaching at least 40% of the vaccinated population by 2021 and 70% by mid-2022.

In the world, so far, 52% of the world population has received at least one dose of the COVID-19 vaccine, but in Peru, meanwhile, 60% of the target population has been exceeded and it has already been started the application of the third dose in some groups.

This advance brings back the debate about the necessary number of people who should be immunized against covid so that those who cannot receive the vaccine – for medical reasons, for example – are also protected. This concept is known as an indirect protection to a small group of unvaccinated due to the high rate of immunization in a given place.

Is it a goal that we must pursue?

After almost a year of the start of immunization campaigns in the world, some experts and health entities should be the main target of vaccination. And it is that, they affirm, we do not really know what percentage of the population will need to be vaccinated until we reach it, or if the same number will be the same for all countries, since the realities are different.

Epidemiological models carried out during the first year of the pandemic spoke of 70% of those vaccinated to achieve this group immunity; The WHO said at the end of 2020 that, while the Vaccination Association in Spain (AEV) placed the number at 75%.

As we showed in a previous report, entities such as the Infectious Diseases Society of the United States and various studies indicated, in the middle of this year, a higher goal:. In the country, the Ministry of Health raised between 75 and 80%.

Beyond the numbers, the experts consulted by El Comercio indicate that, and it will be difficult to achieve due to the characteristics of the vaccines (different technologies and efficiencies), the emergence of variants and the advance of vaccination coverage in each region.

“The concept of herd immunity was developed for some vaccines and for well-known diseases, such as measles. With this disease, when we vaccinate at least 95% of children under the age of five,”, says Jarbas Barbosa, deputy director of the Pan American Health Organization (PAHO), in response to El Comercio.

“For COVID-19, we have vaccines that are different: they have different efficacy and effectiveness; we have different variants… It is a completely different scenario. This concept of herd immunity cannot be applied to any percentage of vaccination that has already been achieved. N, according to some models, it is sufficient. What we are sure of is that we have to continue vaccinating. We have to wait”, details.

The WHO, in this line, remarks that the primary objective is to reach the largest number of vaccinated people. Of the same opinion is the director of the Oxford Vaccine Center, Andrew Pollard, one of the creators of the Oxford / AstraZeneca vaccine, who pointed out that achieving group immunity with the presence of variants such as Delta, so the campaigns Immunization should not have this central objective, but move under the idea that vaccines will stop COVID-19 from being an epidemic and will become an “endemic” disease, such as dengue or seasonal flu.

A no-minor detail cited by experts is that there are already countries in which it has exceeded 70% and has even reached almost 90% of immunized against COVID-19, but the circulation of the virus, although it has dropped dramatically with respect to countries with lower coverage rates,

In sum, the experts and entities agree that the countries, which will allow the health systems not to become saturated again and that activities can be resumed under the new normality.

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