According to a specialist, it is not yet possible to determine the total period that the antibodies remain; studies, however, indicate that immunization persists for at least six months
On January 17th, immunization against Covid-19 began in Brazil. Currently, two vaccines are being applied to the population: CoronaVac, developed by the Chinese pharmaceutical company Sinovac, in partnership with Butantan Institute, in São Paulo, and that of AstraZeneca, manufactured in conjunction with Oxford University. However, there are still many doubts about the vaccines against the coronavirus. One of the main concerns the total duration of immunity. According to the director of the Brazilian Society of Immunizations (SBIm), Flávia Bravo, it is still not possible to determine the total protection time for vaccines that are being used in the country. “This information, and this goes for all vaccines, comes with observation over time. The manufacturers analyze from the beginning of phase 3 of studies until the time after the application of the doses. Therefore, there is no vaccine that has been applied for so long that it gives final, categorical information about the duration of protection offered by the immunizer, ”he says.
In an interview with Young pan, the doctor explains that the follow-up is based on the amount of antibodies after vaccination and the time of occurrence of the disease after the individual completes the vaccination schedule. “So if those people who have already been vaccinated a year, two years, six months, whatever the time, get sick, it is because there was a drop in protection,” he exemplifies. An observation study published in the New England Journal of Medicine points out that the vaccine of Modern maintained antibody levels after six months of application. The ongoing phase 3 clinical trial conducted by Pfizer and for BioNTech indicates that the protection of the immunizing agent developed by the companies also lasts at least six months after the second dose.
Regarding CoronaVac, Sinovac CEO Yin Weidong told the Global Times which studies will be carried out soon to analyze the amount of antibodies in vaccinees after six months. “The current figures show that the protection rate for Sinovac vaccines, within two months after giving two injections, is 80-90%, but the number of antibodies in the recipients decreases over time. We are now analyzing data on protection rates after six months, as well as conducting experiments on the administration of the third dose to see if there is a higher level of protection. Some results are expected to come out soon, ”said Yin Weidong. The doctor Flávia Bravo points out that the emergence of new variants of the coronavirus can also impact the immunity offered by vaccines. “For now, the data suggests that both the AstraZeneca vaccine and CoronaVac are getting P.1, the Brazilian variant of the coronavirus. But, if we do not vaccinate the majority of the population quickly, we give the chance for the viruses to circulate and for new variants to appear, and, with that, a new variant that may escape the vaccine may emerge ”, says the doctor.
Will Covid-19 vaccines be reinforced every six months or annually?
The need for a semi-annual or annual renewal for vaccines against Covid-19 depends exactly on the duration of the protection offered by them and the emergence of new variants. In other words, there is still no definitive answer from the scientific society to the question. “This is not just for vaccines against Covid-19. It happens to everyone. The tetanus vaccine, for example, we need to have boosters every 10 years because the level of antibodies decreases after that time. When meningococcal vaccines, which are newer, appeared, we didn’t know if a renovation would be necessary ”, exemplifies Flávia. “Meningo-b, in this case, we still don’t know if there is a need for reinforcement because we didn’t have the adequate observation time for that. With meningococcal A, G, W and Y, we already know that the protection time is around five years in children. In the case of the hepatitis B vaccine, it was believed that a booster would be needed. Nowadays we know that you don’t have to, except for special patients. ”
The director of SBIm emphasizes that the need for reinforcement is not a demerit of vaccines. “If there is to be reinforcement, so be it. We already have experience, it is something that can happen. It depends on the type of disease, the degree of protection from antibodies and cellular immunity and how much these vaccines are able to stimulate memory. There are several factors that interfere with this information, which will only arrive with time for us ”, he adds. Even with high immunity, it is still possible for a person to contract the coronavirus even after being vaccinated. “These vaccines, all of them demonstrated good efficacy in preventing the disease, which is what we need. But none is 100% and the person can still contract the virus. Can an infection happen? He can. But the vast majority, with some exceptions, are asymptomatic or have a mild form of the disease. Anyway, even if I get sick, I will have a light picture of Covid-19 ”, he explains. According to the doctor, however, the biggest concern at the moment is to control the epidemiological situation, that is, to reduce the circulation of the virus so that it stops spreading and, thus, to reduce the number of deaths, hospitalizations and patients who need medical evaluation, relieving the health system.