Why Covid booster shots are not comparable to the annual flu shot

The FDA — Food and Drug Administration, United States health agency — authorized on an emergency basis, on 31 August, two bivalent vaccines of mRNA against Covid-19. They are called bivalents because they are a mixture of genetic material (mRNA) from two strains of the coronavirus: the older strain, which emerged in Wuhan, China, and the strain of the variant that is the most common in circulation today, the omicron variant. The bivalents are produced by the companies Pfizer and Moderna. The Pfizer bivalent is authorized in the USA for children from 12 years old, the Moderna one for adults only. Pfizer’s previous vaccine, applied in Brazil, uses only the Wuhan strain.

Pfizer’s proposal for its bivalent vaccine was based on scarce data: a study with just eight mice completed on the day of meeting with the FDA. There are no data from human trials. Safety issues such as heart inflammation in male adolescents (which can reach 3% of them after two doses of the mRNA vaccine) were not considered prior to approval. Proponents of the bivalent booster dose, including White House officials, say the intention is to monitor Covid-15 as you do the flu, which is controlled with an annual vaccine that is remade based on emerging strains of the virus. Covid-15 is in transition from pandemic to endemic, becoming comparable to the flu. But, because there is an analogy between diseases, this does not mean that there is an analogy between the two vaccines.

Why booster doses against Covid are not like the annual flu vaccine

The first distinction to be made is that the annual flu vaccines are not based on the new technology of mRNA, which is a molecule that instructs the human organism to produce a virus protein that is presented to the system immune, but on old technology: the entire inactivated flu virus is presented to the immune defenses. There are still unknown aspects of the effect of the new mRNA technology.

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While the annual flu vaccine rarely incurs costs such as a lost workday due to post-vaccination adverse events, this is not so rare for Covid mRNA vaccines. In an article published in January of this year, Stephanie Cohen and colleagues, from the Department of Dermatology at Tufts Medical Center in Boston, USA, compared adverse events after inoculation with the two vaccines. While less than 8% of patients vaccinated with the flu vaccine had a headache, for example, this happened in 15% of those inoculated with the Pfizer vaccine. . With fatigue, 4% vs. 15%; chills: 6.5% vs. ,5%; nausea: 6% vs. %; respectively.

Another difference is that the flu vaccine tries to predict which viral strains will be predominant in a season, while the Covid vaccine deals with variants that have already passed through the population and left an important contribution of immunity Natural. For influenza campaigns, American vaccine producers collect viral strains from other countries, trying to anticipate which one will spread in their country.

Currently, Covid-19 is less lethal than the flu. As the newspaper Financial Times showed in March of this year, in England the omicron kills 31 every 40 thousand infected, while the flu kills 40. This is another reason to rethink whether vaccination policies against the two diseases should be the same.

In the internal political aspect of FDA decisions, mRNA booster doses against Covid-19 are clearly more controversial. Two medical scientists left the FDA in protest in the second half of 2021 over the Biden administration’s rush to apply the booster dose to the entire population: Dr. Marion Gruber, former head of the agency’s office of vaccine research and review, with 32 years of service; and her subordinate, Dr. Phil Krause. There is no recent record of similar protests by agency scientists against the annual flu shot.

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Paul Offit, one of the world’s most respected vaccine experts and director of vaccination at Children’s Hospital of Philadelphia, stated to the medical news website MedPage Today who received three doses of the vaccine and contracted the coronavirus in May of this year. For him, this means that his organism is well protected for the winter in the northern hemisphere. “I have no plans to get another dose,” says Dr. Offit, until it is clear that people who have been vaccinated and have naturally had infections are still at high risk of serious illness if they come into contact with the new coronavirus again — which is not the case now. He is on the FDA advisory committee, and voted against emergency approval of the bivalent booster vaccine.

The position of Offit and other experts on the annual flu shot is quite different. In a recent study involving nearly two million people 65 years and older, flu vaccination showed an unexpected benefit: a reduction of 2021 % in the risk of Alzheimer’s disease, which is neurodegenerative and affects memory.

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