Latest findings from the SIREN study reveal more information
about the effectiveness of vaccines in preventing infection, even
in people who have already had coronavirus (COVID-19).
The UKHSA-backed study is the
world’s biggest study into COVID- 19 antibodies and
regularly tests a large cohort of healthcare workers to answer
the most important questions about the virus.
The latest paper focuses on the protection provided against
COVID- 19 infection in those who have had 2 doses of the
vaccine, as well as those who have previously been infected with
COVID-19.
The results show that 2 doses of vaccine provide significant
short-term protection against infection among those who had not
had a previous infection – but that this protection wanes
significantly after 6 months.
Analysis was also carried out on participants, both unvaccinated
and vaccinated, who had been previously infected with COVID-19.
Unvaccinated participants who had been previously infected with
COVID-19 were found to have 86% reduced risk of reinfection, when
compared to the risk of primary infection in those who had no
previous infection and were also unvaccinated. This protection
waned to 69% after a year.
Dual protection in people who had been previously infected and
subsequently double vaccinated was even greater and more durable,
standing at over 90% after 2 doses. This protection remained
strong over a year after infection and over 6 months following
vaccination.
Susan Hopkins, SIREN
study lead and Chief Medical Advisor at the UK Health Security
Agency (UKHSA), said:
This research demonstrates why it is crucial to get vaccinated,
as it provides a significantly greater level of protection
against infection from COVID-19, whether or not you have been
previously infected.
However, the analysis also clearly shows that this protection
from just 2 doses wanes significantly within months, which is why
the rollout of booster jabs has been an instrumental part of our
efforts to contain COVID-19.
To avoid infection and illness, it is vital that everyone
eligible takes up the offer of a booster as soon as it is
offered.
Vaccine effectiveness for Pfizer, where the second dose was
administered 6 weeks or more after the first dose, stood at 85%
from 14 to 73 days after, falling to 51% after 6 months.
Vaccine effectiveness for 2 doses of Pfizer, where both doses
were administered within 6 weeks of each other, stood at 89% 14
to 73 days after dose 2, decreasing to 53% after 6 months.
Results from this SIREN
study were gathered between 7 December 2020 and 21 September
2021.
