While it confers greater protection against the virus in the first months after injection, the Pfizer vaccine sees its effectiveness decline more rapidly than that of AstraZeneca.
- After four or five months, the effectiveness of Pfizer and AstraZeneca are similar.
- Despite these slight drops in protection, the overall efficacy of the two vaccines remains very high, say the researchers.
The Delta variant continues to prove itself as a tough opponent for vaccines. To counter it, the vaccine developed by Pfizer and BioNTech is proving effective, although the one manufactured by Moderna offers a higher level of protection against infections. A new study, pre-published and carried out by British researchers from the University of Oxford, suggests that in the face of the Delta variant, the effectiveness of Pfizer declines more rapidly than AstraZeneca.
Similar effectiveness after four or five months
In the first months after the second injection, the Pfizer-BioNTech vaccine provides high protection against high viral load infections. After one month, it rises to 90% against the Delta variant. This will then drop in the months that follow. It increases to 85% after two months and then to 78% at three months. These figures are higher than those of AstraZeneca whose efficiency varies from 67% to 61% during the first three months.
After this period, the protection levels of the Pfizer against the Delta variant fall and join those of AstraZeneca. This occurs around the fourth and fifth months following the second injection. These results were obtained after analyzing samples from more than 700,000 participants between December 2020 and August 2021.
Efficiency that remains high
This numbers “really represent a decline“effectiveness for Pfizer’s vaccine, explained Dr. Koen Pouwels, who worked on the study, while for AstraZeneca”differences (month to month) are random, i.e. there might be no change in coverage.”
The researcher still insisted that despite “those light protection drops, the overall efficacy (of both vaccines) remains very high.“He also points out that the researchers had studied the overall protection and not the level of protection against severe forms and hospitalizations,”two very important data for evaluating the effectiveness of vaccines”.
