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Health The antibodies of the Sinovac vaccine against Covid disappear after 6 months, what happens with the rest of the vaccines?
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The effectiveness of the
Pfizer vaccine
in preventing infection decreases over time, falling,
six months after the second dose, from 96% to 83.7%
.
The effectiveness against severe forms of
Covid
, on the other hand, remains high at 97%.
So is a third dose necessary?
The results
The results of a study published online without a review still say so: efficacy against symptomatic Covid
declines by about 6% every two months
, dropping to 83.7% after six months.
The results come from 42,000 volunteers from six countries who participated in a clinical trial started by
Pfizer
and
BioNTech
last July and ended on March 13.
In the period of one week to two months after the second dose, the effectiveness was 96.2
percent
.
In the period of two to four months, the effectiveness was reduced to 90.1%.
And from four months to six months, the effectiveness reached 83.7%.
The study did not measure the rate of asymptomatic viral infections.
Same find from Israel
The data comes from a time when
the Delta variant
, which makes vaccines slightly less effective against infections, was not as dominant as it is now in hundreds of countries around the world, although recent studies have shown that the
vaccines
are still very protective against the worst of the Covid even with infections caused by Delta.
The new study comes on the heels of a
similar analysis from Israel that suggested that Pfizer's vaccine protection may be waning in the country.
Data published in May by the Israeli health ministry showed an efficacy of the
Pfizer vaccine
equal to 94.3% in preventing asymptomatic infections, while in June, when the
Delta variant
was more widespread, coverage was around 64% .
Compared with severe disease, the efficacy rate was reduced by only 5%.
Pfizer also shares the results of the third dose
With
coronavirus
cases on the rise
in many states, the findings could influence
government decisions about the provision of the third dose,
and drug companies are keen to promote specific studies.
At this time, Pfizer itself shared the results of the trials on the
third dose
of its original vaccine against the
Delta variant
: antibody levels
increased 5 times
between 18-55 years and
11 times
between 65-85 years.
Decisions on the third dose
The decision on the third dose, however, is not unanimous
and there is great uncertainty: in the US the idea is that "fully vaccinated Americans do not need a booster dose at this time", and emphasizes that it does not depend on individual companies. decide if and when the booster will be needed.
Even the European Medicines Agency (EMA) assures that "it is too early to confirm if
and when
a booster dose will be needed for
Covid-19
vaccines
, because there is still not enough data from immunization campaigns and studies."
However, some countries have taken action: Turkey has already started offering a third dose of
Sinovac
(or Pfizer) to some people.
Indonesia and Thailand have agreed to give the third dose of
Moderna
and
Pfizer
to some people vaccinated with CoronaVac.
Many are considering the third dose for the elderly and immunosuppressed.
According to the criteria of The Trust Project
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Coronavirus
Covid 19
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