The United States of America applies the third dose of Pfizer and Moderna vaccines

Photo: Mario Tama/AFP – 25/6/21

With the United States returning to record more than 1,000 deaths a day from Covid-19, the Centers for Disease Control and Prevention (CDCs) announced yesterday that Americans vaccinated with mRNA-based immunity (Pfizer/BioNTech and Moderna) may receive a third dose from September 20 . To justify this measure, the agency’s director, Rochelle Walinsky, issued a statement signed by other health authorities, noting that although it is “extremely effective in preventing hospitalization,” the material loses, over time, its potential to protect against SARS. -2.

Yesterday, the Centers for Disease Control and Prevention released three new studies that indicate the efficacy of mRNA vaccines declines over time. One of them, done with residents of nursing homes, found that two doses of these immunizations were 74.7% effective against infection at the start of the vaccination programme. “During the period from June to July 2021, when trading of the B.1.617.2 (delta) variant prevailed, the effectiveness decreased significantly to 53.1%,” the article says.

Another survey, with data from New York State, indicated that the effectiveness of vaccines against hospitalization decreased from 91.7% between May and July, to 79.8%. The third study released by the Centers for Disease Control and Prevention (CDC), which included 1,129 patients who received two doses of the immunizing agent from Pfizer or Moderna, found no reduction in the substance’s protection within 24 weeks.

Vaccine efficacy was 86% between 2-12 weeks after vaccination and 84% between 13-24 weeks. Vaccine efficacy was maintained among groups at risk of severe COVID-19”, says the article. Rochelle Walinsky considered the result “excellent”.

According to the joint statement — which is endorsed by the FDA, and which has the final say — who received the second injection eight months ago, he will be scheduled for booster. “Available data show that protection against SARS-CoV-2 infection begins to wane over time after initial vaccination doses, and in combination with delta-variable control, we are beginning to see evidence of reduced protection against mild to moderate disease,” the statement says.

“For this reason, we conclude that a booster injection will be necessary to maximize vaccine-induced protection and prolong its durability.”

According to the Centers for Disease Control and Prevention, the primary beneficiaries of this increase are residents of nursing homes, the “advanced age”, and health professionals, as happened at the start of the Covid immunization program last December. In addition to the mRNA vaccines, the statement indicated that a booster would likely be needed for people who received a single dose of Janssen’s immunosuppressant.

Who is the

The idea of ​​an additional dose before completing a year from the second injection does not satisfy the World Health Organization (WHO), which yesterday again opposed the boost. “We clearly think that the current data does not indicate a need for boosters,” said chief scientist Soumya Swaminathan, adding: “We have to wait for the science to say when boosters will be needed, for which groups of people and for vaccines.” Criticisms of the World Health Organization are directed at rich countries. that takes the third dose, while many countries fail to get the ‘first injection’.

Although studies released by the Centers for Disease Control and Prevention show a decrease in the effectiveness of mRNA vaccines over time, the percentages of protection remain satisfactory – for the immune system to be considered effective, it must have a level of protection above 50%. Israel announced the third dose for the elderly, and the UK plans to give a booster dose to the general population soon.

However, some experts are not convinced of this need. The first scientific question is: Do we have evidence that a third booster dose is needed? The real need is not to reduce the number of mild cases, although their impact should not be underestimated, but rather to reduce hospitalizations and deaths among those who have already received two doses,” says Stephen Evans, Professor of Epidemiology at the School of Hygiene and Tropical Medicine from London.

Evins points out that no Covid vaccine is 100% effective in preventing all types of infections. “But we have no evidence that there is now a sharp increase in hospitalizations and deaths among those who took two doses.”