The US companies Pfizer and Moderna have announced that the protection provided by their respective coronavirus vaccines may weaken over time. This announcement – probably not accidentally – comes at a time when the US Food and Drug Administration (FDA) is preparing to decide whether to approve a broader booster program.
Pfizer, according to the Financial Times and Reuters, presented a study by the Kaiser Permanente Medical Center in Southern California, which shows that the effectiveness of its vaccine tends to weaken naturally over time, “regardless of the coronavirus variant” and not as a consequence of the Delta strain.
According to this research, the vaccine's immune protection decreases six to eight months after the second dose. The reduction was estimated at about 6% every two months after the second dose, falling from 96.2% shortly after vaccination to 83.7% four months after the second dose . The company also cited data from another Israeli study, according to which the third dose restores the vaccine to 95% effectiveness.
Moderna, for its part, has presented evidence from a major clinical trial that the protection of its vaccine weakens over time, supporting the usefulness of an extra booster dose. The study found higher rates of Covid-19 infections among those who were first vaccinated 13 months ago than those who were vaccinated eight months ago.
However, a second study, in collaboration with the Kaiser Permanente health system, which compared some 352,000 fully vaccinated with Moderna to a similar number of unvaccinated, found that its vaccine, even in the midst of Delta spread, remained 87% effective against of Covid-19 infection and 96% of the risk of hospitalization.
As Moderna President Stephen Hawth stated, “The first six months (of protection) are important, but one can not 'bet' that this (protection) will remain stable for a year or more.” As he said, “as autumn and winter come, we expect the estimated weakening of immunity to lead to an additional 600,000 additional cases of Covid-19, ” although he did not estimate how many of these cases could be serious and require hospitalization. He added that “boosting doses will reduce Covid-19 cases. We also believe that a third dose has the opportunity to significantly extend immunity throughout the next year. “
Moderna's new “narrative”, however, contradicts recent studies, according to which its vaccine provides longer-term protection than that of Pfizer / BioNTech.
The FDA's advisory committee will meet on Friday to decide whether to recommend boosting doses and to which segment of the population, a decision that is eagerly awaited, if not anxiously. The FDA has already approved extra doses of mRNA vaccines for those with weakened immune systems for medical reasons.
Both Pfizer and Moderna have applied for a third installment. So far the scientific community seems rather reluctant to approve this request, considering that there is insufficient evidence.
Source: ΑΠΕ-ΜΠΕ
