Covid: Why Brazil does not recommend AstraZeneca and Janssen – 04/12/2023 – Health

The Ministry of Health no longer recommends the use of viral vector vaccines (AstraZeneca and Janssen) as a booster against Covid-19.

Viral vector vaccines are created from a type of adenovirus that does not harm human health.

Inside it, scientists insert some Sars-CoV-2 genes, causing the immunity of those who received the dose to be trained against the cause of Covid-19 without receiving the damage from the infection.

Anyone who has taken any of the vaccines, however – either as a first dose or a booster – should not be concerned.

The interruption of the use and production of immunizer by the Ministry of Health has nothing to do with effectiveness, but with a possible increased risk of thrombosis days after vaccination, according to a document published by the Ministry of Health.

The Ministry of Health informs that, until September 17, 2022, 98 cases (0.02 cases per 100,000 doses applied) were notified in the e-SUS — excluding data from São Paulo, which were not disclosed in the document — suspected Thrombosis Syndrome with Thrombocytopenia (drop in platelets) in temporal relation to vaccines.

Of these cases, according to the agency, 34 were attributed to viral vector vaccines, 17 cases were recorded as having a probable relationship and 47 occurrences were considered possible cases.

The conditions, which were more common in women, occurred within a maximum period of 30 days after application. Those who received the dose a longer time ago and did not develop thrombosis are not considered at risk related to the vaccine.

BBC News Brasil asked pharmaceutical companies AstraZeneca and Janssen for a position, which signaled to receive the request, but did not send a response until the time of this publication.

Why could viral vector vaccines cause thrombosis?

“There is a possibility that some people —and we have no way of identifying this individually— have a very personal genetic characteristic, which in contact with these viral vector vaccines, favors hypercoagulability, favoring the creation of thrombi”, explains infectologist Evaldo Stanislau de Araújo, from the Hospital das Clínicas in São Paulo.

According to the document from the Ministry of Health, “due to the rarity of occurrences, it has not yet been possible to identify risk factors associated with the syndrome, with the exception of an apparent increased risk in individuals aged below 40 years of age”.

In the evaluation of immunologist Gustavo Cabral, it is not possible to say with confidence, precisely because of the lack of clarity in the association, that vaccines are responsible for cases of thrombosis.

“The scientific studies I’ve been reading are very good, but a lot of explanation is missing for how the vaccine will be the trigger”, points out he, who is a researcher at the University of São Paulo and FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo ).

Despite the lack of detailed explanation, Cabral understands that the Ministry of Health’s decision is reasonable at the current epidemiological moment, in which viral vector vaccines are not indispensable as they were at the height of the pandemic.

Viral vector vaccine fulfilled its role at critical moment

Among the possible consequences of a Covid-19 infection is precisely the creation of thrombi – with an incidence even much higher than the correlation made with viral vector vaccines.

A study published in the scientific journal Radiology shows that, among 3,342 infected with Covid-19 who required hospitalization, the thrombosis rate was 16.5%.

“In 2021, when the possibility of these vaccines causing thrombotic conditions arose, we were at a time when there was little supply of immunizers and in the face of a disease that is characteristic of causing thrombosis. Failing to vaccinate with a vaccine that would hypothetically cause the condition would not be correct in time”, evaluates the infectologist.

“This reasoning, in 2023, is no longer valid. The benefit of the vaccine today is lower and it is unacceptable to offer thrombotic risk. A large part of the population is vaccinated with multiple doses, that is, we have a protected population and a greater offer of vaccines. It is unreasonable to do the same analysis.”

The current recommendations

The production of AstraZeneca vaccine serum by Fiocruz, which had an agreement to produce a nationalized version of the vaccine, was stopped.

Most patients were under 40 years old, and therefore the official recommendation presented in the document for viral vector vaccines.

Cabral also draws attention to the fact that, after an initial dose of viral vector vaccine, it is best to use another type of technology for reinforcement.

“These viral vector vaccines carry information from the virus to our cells. In subsequent doses, this information arrives less effectively.”

What are thrombi and why are they dangerous?

Thrombi are blood clots formed in veins or arteries that hinder blood circulation and can appear in different parts of the body.

Depending on the location and size, clots can be considered more dangerous. In the lungs or brain, for example, they can block vital blood flow and lead to permanent damage and even death.

The report points out that the most frequently reported clinical form was cerebral venous thrombosis. There are also reports of intra-abdominal vein thrombosis, pulmonary thromboembolism and arterial thromboses.

Guidance follows recommendation from other countries

Different countries have already adopted restrictions on the indications for the use of viral vector vaccines.

Currently, the CDC (Centers for Disease Control and Prevention) in the United States recommends that the Janssen vaccine be used only in situations where there is a contraindication for the use of other vaccines, in situations of limited access to other vaccines or for individuals who wish to vaccinating with Janssen despite safety concerns.

The NHS (National Health Service), UK public system, indicates the preferential use of Pfizer or Moderna vaccines for people under 40 years old. In Canada, viral vector vaccines are indicated only when there is a contraindication to the use of other vaccines authorized in the country.