the essential A study by the laboratory and the American health network Kaiser Permanente analyzed the effectiveness of the Pfizer vaccine. The latter would be effective against the most serious forms of Covid – 19 as well as against the risks of hospitalizations. However, its efficacy against Delta variant infection would decrease four months after full vaccination.
Effective against severe forms and the risk of hospitalization for at least six months
The Pfizer vaccine indeed effective against severe forms of Covid – 19? According to a study published this Tuesday, October 5 in the journal The Lancet and taken up by Le Parisien, the vaccine would be effective against the risk of infection at 88% in the following month injection ending the vaccination schedule, against 19% after six months. Its effectiveness against the risk of infection therefore decreases over time.
The study analyzed the medical data of 3.4 million people, between December 4 2020 and August 8 2021, in California . It also shows that the vaccine remains effective at 90% against the risks of hospitalizations linked to the virus for at least six months. Efficacy that includes cases of delta variant infection.
“Our study confirms that vaccines are a central tool in controlling the epidemic and remain extremely effective in preventing severe forms and hospitalizations, including against Delta or other variants of concern” explains Sara Tartof, lead author of the study , at the Parisian. The results obtained by the scientists indeed confirm the estimates of the American Center for the control and the prevention of the diseases and of the Israeli Ministry of Health.
Efficacy against Delta variant infection decreases after four months
According to this study, the efficacy of Pfizer vaccine against Delta variant infection would be 93% during the first month after complete vaccination. Efficiency that would drop to 53% after four months. This fall is “probably” due to the time that passes after the second injection. The very nature of the Delta variant then had nothing to do with it, “since the efficacy of the vaccine against Delta infections was more than 90% shortly thereafter vaccination “.
Towards the third dose?
“A specific analysis of the variants clearly shows that the vaccine is effective against all kinds of variants. People infected with Covid – 19 who had received two doses vaccine were most often because of a loss of efficacy of the vaccine over time and not because a particular variant escapes the protection of the vaccine “details from the Paris daily Luis Jodar, vice-president and Chief Medical Officer at Pfizer.
According to the authors, “booster doses may possibly be needed to restore the high levels of protection observed at the start of the vaccination program.” The results allow the vaccine’s effectiveness to be analyzed over time, a way the scientists say can determine which parts of the population could be prioritized for booster doses.