Mexico is administering Covid-19 vaccines developed by pharmaceutical companies Pfizer, AstraZeneca, Sputnik, Sinovac, and CanSino.
When will we have to get vaccinated against Covid-19 again? This is one of the questions we ask ourselves the most now that people are being vaccinated against the coronavirus.
In Mexico, more than nine million doses have been administered so far to health workers and adults over the age of 60, according to information from the Mexican government.
Now that people are being vaccinated, they’re beginning to ask, “When will we have to get vaccinated again, either as a booster for the initial dose or to start generating new antibodies that protect us against SARS-CoV-2?”
There’s no single answer so far. In addition to the information published by the laboratories that developed vaccines for emergency use, the few answers that exist come from the global scientific community which is collaborating in the fight against the pandemic.
Initial data from scientific analyses indicate that protection after vaccination can last from three to six or eight months, although most experts who have been studying this have said that it’s too early to be sure of an immunization period.
Another factor that needs to be taken into account for determining the period of protection has to do with the behavior of the vaccines against new variants of SARS-CoV-2.
So far, Pfizer is the only laboratory to have published data on the immunization period of its vaccine, developed in conjunction with the BioNTech laboratory.
Protection from this vaccine would last for at least six months after application of the second dose, the company reported in a non-peer-reviewed statement.
The company said that this result, obtained from its ongoing phase 3 clinical trials, is better than the initial estimate of 90 days’ immunity.
Pfizer’s vaccine offers 91% protection after applying the second dose, which offers one of the highest levels of those currently used in Mexico.
Our CEO, @AlbertBourla sharing #Covid19 vaccine manufacturing updates from our Kalamazoo, Michigan site after @POTUS stopped by. #ScienceWillWin cc:@WHCOVIDResponse Watch here ? pic.twitter.com/BNRFhAsTUS
— Pfizer Inc. (@pfizer) February 19, 2021
The Russian vaccine, developed by the Gamaleya Research Institute of Epidemiology and Microbiology at the Russian Ministry of Health, starts off with an efficacy of 91.4% against Covid-19 infection.
However, the level of neutralizing antibodies may decrease over time after the two recommended doses have been received.
In the case of Sputnik V, the first data suggest that efficacy remains at 70% after 150 days, while it decreases to 50% after 255 days, according to the results of studies carried out by researchers from the Kirby Institute of the University of South Wales, in Australia.
The Mexican government vaccination study confirms that #SputnikV is the safest among all vaccines used in Mexico with 7 times fewer adverse effects than the Pfizer mRNA vaccine. The Mexican data supports similar results published by the government of Hungary on April 25. pic.twitter.com/ql9CZwp9r0
— Sputnik V (@sputnikvaccine) April 26, 2021
Last month, pharmaceutical company AstraZeneca adjusted the efficacy of its vaccine against Covid-19 virus infection to 76%, following a complaint from the Food and Drug Administration (FDA).
According to the Kirby Institute’s results, the vaccine developed in conjunction with the University of Oxford would have an efficacy of 50% after 50 days from application of the second dose.
Both vaccines were developed in China. Sinovac offers a 50% immune response against Covid-19, although response time after application is still unknown.
The same is true for the CanSino vaccine.
The World Health Organization (WHO) has indicated that it is still too early to know for certain how long someone vaccinated against Covid-19 is protected for.
Official statements from the WHO have indicated that most vaccines are still in the stages of clinical analysis, so it’s not possible to determine how long they offer protection against Covid-19.
However, it considered that the response the vaccines have had against the virus to be encouraging, and that time must be allowed to pass to know how long the immunity they offer lasts.
Even so, different investigations suggest that immunity against Covid-19 from vaccines could be from one to two years. In some cases, it cannot be ruled out that there is even a possibility of it being for life. The scientific community is also studying so-called cellular memory.
Cellular memory is the reaction that a vaccine induces through T lymphocytes, which are in charge of the immune response through cells, and B lymphocytes, which are responsible for the immune response through antibodies.