Pfizer vaccine against Covid-19: its effectiveness against the risks of hospitalizations remains at least six m

These results, which come from a study published Tuesday in The Lancet , show, according to its authors, the importance of strengthening global vaccination and analyzing the effectiveness of the vaccine over time to decide which populations should be prioritized for booster doses.

Two doses of Pfizer / BioNTech vaccine are effective against the risks of hospitalization linked to Covid-19 and all its variants for at least six months, indicates a study published on Tuesday, October 5 in the journal The Lancet , confirming previous estimates. To arrive at this figure, Pfizer and the American health network Kaiser Permanente analyzed the medical data of 3.4 million people in Southern California between December 4, 2020 and August 8, 2021.

The vaccine thus remains 90% effective against the risks of hospitalizations linked to Covid-19, including in the event of infection with the Delta variant, for at least six months, she emphasizes. On the other hand, the effectiveness of the vaccine against the risks of infection decreases over time, going from 88% in the month following the injection of the second dose to 47% after six months.

The vaccine, “a central tool for controlling the epidemic”

These results confirm the results of previous estimates from the US Centers for Disease Control and Prevention (CDC) and the Israeli Ministry of Health, points out. The Lancet in a press release. “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,” summarized Sara Tartof, lead author of the study, cited in the press release.

“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 of the vaccine were most often affected due to loss of effectiveness of the vaccine over time and not because a particular variant escapes the protection of the vaccine “, also underlined Luis Jodar, vice-president and chief medical officer at Pfizer.

The researchers recognize some biases in their survey: for example, they did not have data on the respect of wearing a mask, social interactions or the profession of the populations studied, which could have an impact on the probability of contracting the Covid. -19.

According to the study’s authors, these results show the importance of scaling up global immunization and analyzing vaccine effectiveness over time to decide which populations should be prioritized for booster doses.