Pfizer and Moderna vaccines used as a third dose provide the best overall booster responses, according to a UK study of seven different vaccines.
In the study, all vaccines tested increased immunity against Covid to some degree. The researchers evaluated the boost (third dose) after two doses of Oxford-AstraZeneca or two doses of Pfizer.
The study justifies the UK’s initial decision to use these two vaccines for booster shots.
In Brazil, according to the Minister of Health, Marcelo Queiroga, the trend is that most adults receive the Pfizer product as a third dose (read more below).
The researchers said there were promising signs that the boosters still protect against illness and death caused by the omicron variant.
To expand the supply of vaccines, even half a dose of Pfizer’s vaccine could be used for the boost, they added.
The trial results are believed to have prompted the UK to request an extra 114 million doses of Pfizer and Moderna vaccines, to be used over the next two years.
Booster doses can reduce the risk of infection by more than 93%. In both Brazil and the UK it has been announced that all adults over the age of 18 will be able to receive a booster dose — as scientists try to find out more about the omicron variant.
Earlier this week, Pfizer’s CEO said booster shots against Covid could become an annual event.
In the study of nearly 3,000 adults — led by the University of Southampton (UK) and published in the journal Lancet — booster doses were given about three months after the second doses of AstraZeneca or Pfizer.
Of seven different vaccines tested ——including Janssen, Oxford-AstraZeneca, Novavax, Valneva, CureVac—, all were found to be safe.
The seven vaccines boosted immunity when given after two doses of Oxford-AstraZeneca, and six were effective after two doses of Pfizer — but some worked better than others.
Overall, the mRNA vaccines —Modern and Pfizer— gave the best boost to antibodies and T cells, which are known to be important factors in the proper functioning of vaccines, especially after two initial doses of AstraZeneca.
Vaccines were equally effective in people over 70 and under 70 years of age.
The researchers say they have found a strong response to all virus variants, including alpha, delta and the original strain, and hope this translates into protection against omicrons as well. However, they caution that more data will be needed to find out what this means for long-term protection against serious illnesses.
In people who received two doses of AstraZeneca, the study found a 30-fold increase in antibody levels after boosting with Moderna and a 25-fold increase after boosting with Pfizer.
After two doses of Pfizer, which offers higher baseline protection, the same vaccines maximally increased antibody levels.
‘Encouraging’
Professor Saul Faust, who led the study at the University Hospital Southampton NHS Foundation Trust, said: “It’s really encouraging that a wide range of vaccines, using different technologies, show benefits like a third dose for AstraZeneca or Pfizer-BioNTech. and flexibility in developing reinforcement programs here in the UK and globally.”
On protection from hospitalization and death from the micron, Faust said he hopes it “remains intact” and “is treated with current vaccines.”
Jonathan Ball, professor of molecular virology at the University of Nottingham, added that the study clearly shows that “all types of boosters increased at least one aspect of immunity against Covid.”
Oxford-AstraZeneca vaccine is being used in over 180 countries and Pfizer is being used in over 145 countries.
Third dose in Brazil
In mid-November, the Ministry of Health announced that all Brazilians over 18 are able to take a third dose of the vaccine that protects against Covid-19.
Until that moment, the booster took place after six months and was only indicated for individuals over 60 years old, health professionals and immunosuppressed (people with problems in the immune system).
Minister Marcelo Queiroga assured that the country has enough doses to offer this third application to all adults between November 2021 and May 2022, at 38 thousand health centers throughout the country.
At the time, when asked about the type of immunizing agent that will be used as a booster, Queiroga said that the ministry continues to bet on the heterologous scheme.
“The preference is for this additional dose to be a different vaccine, which is a decision based on data and scientific evidence,” he explained.
In other words, this means that anyone who has taken two doses of AstraZeneca will receive a third from Pfizer and vice versa.
The trend, according to the minister, is that most adults receive the product from Pfizer as a third dose, because the immunizing agent from AstraZeneca was the most used as the first and second doses in this age group over the past few months.
“In the event of a possible shortage of Pfizer’s vaccine, which should not happen, we will be able to use another vaccine platform, preferably of a different type than the one used in primary vaccination”, completed Queiroga.
Physician Rosana Leite de Melo, extraordinary secretary for Covid-19 at the Ministry of Health, said that Brazil has already guaranteed enough vaccines to apply the third dose and is already evaluating the need to buy more units for an eventual fourth dose in the elderly in the second half of 2022.
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