When will we have to vaccinate again against Covid-19?

The effectiveness time of the different vaccines against Covid-19 is one of the questions that the scientific community studies in the fight against the pandemic. (Photo: iStock)

When will we have to vaccinate against Covid-19 again? It is one of the questions we ask ourselves the most now that vaccination against the coronavirus is underway.

In Mexico more than nine million doses They have been applied so far to medical personnel and adults over 60 years of age, according to information from the Government of Mexico.

With vaccination underway, the question now is When will we have to vaccinate again? Either to reinforce the initial dose or to start a new process to generate protective antibodies against SARS-CoV-2.

When will we have to vaccinate against Covid-19 again?

There is no single answer so far, because in addition to the information that the laboratories that developed vaccines for emergency use have made public, the few answers that exist come from the world scientific community that collaborates in the fight against the pandemic.

The first known data from scientific analyzes indicate that the duration of protection after vaccination can range from three to six to eight months, although most experts focused on this have said that it is early to ensure a period of immunization.

Another factor that includes to determine the period of protection has to do with the behavior of the vaccines against new variants of SARS-CoV-2.

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So far Pfizer is the only laboratory that has released data on the duration of your vaccine immunization, developed together with the laboratory BioNTech.

The protection of this vaccine would be at least six months following the application of the second dose, the company reported in a non-peer-reviewed statement.

The company estimated that this result, obtained from its ongoing phase 3 clinical trials, is better than the initial 90 days of estimated immunity.

The Pfizer Vaccine offers 91% protection after applying the second dose and it is one of the highest currently applied in Mexico.

Sputnik V

The vaccine of Russian origin, developed by the Gamaleya National Research Center for Epidemiology and Microbiology, from the Ministry of Health of this country, starts with an efficiency of 91.4% against Covid-19 infection.

However, the level of neutralizing antibodies may decrease as time passes since the two recommended doses were received.

In the case of Sputnik V, the first data suggest that after 150 days the efficiency remains at 70%, while after day 225 it decreases to 50%, according to the results of studies done by researchers from the Kirby Institute of the University of South Wales, in Australia.

AstraZeneca / University of Oxford

Last month, the pharmaceutical AstraZeneca adjusted the effectiveness of your vaccine against Covid-19 to 76% against virus infection, following a complaint from the Food and Drug Administration (FDA).

According to the results of the Kirby Institute, the vaccine developed in conjunction with the University of Oxford it would be 50% effective after day 50 of the application of the second dose.

Sinovac and CanSino Biologics

Both developmental vaccines in China, in the case of Sinovac offers a 50% immune response against Covid-19, although the response time after its application is still unknown.

The same is true for the Sinovac vaccine.

What does the WHO say?

The World Health Organization (WHO) He pointed out that it is still too early to know the time in which a vaccinated person is protected against Covid-19.

In official communications, the WHO has indicated that since most vaccines are still in the stages of clinical analysis, It is not possible to determine the time they offer protection against Covid-19.

However, he considered that the response that vaccines have had against the virus is encouraging and that it will take time to give an answer on the immunity time they offer.

Even in the face of this, and that different investigations suggest that the immunity of vaccines against Covid-19 could be from one to two years, and even in some cases the possibility that it is for life is not ruled out, the scientific community also bet on the call cellular memory.

Cellular memory is the response that a vaccine induces through the T lymphocytes, responsible for the immune response through cells, and the B lymphocytes, responsible for the immune response through antibodies.