February 22, 2021

expert reaction to new reports from PHE on Pfizer-BioNTech vaccine effectiveness data and the SIREN study

New reports from PHE on the early impact and effectiveness of COVID-19 vaccination in England, and on the effectiveness of the Pfizer-BioNTech vaccine against infection and COVID-19 vaccine coverage in healthcare workers in England (the SIREN study) have been published today.

This Roundup accompanied an SMC Briefing.

Dr Peter English, Consultant in Communicable Disease Control, Former Editor of Vaccines in Practice Magazine, Immediate past Chair of the BMA Public Health Medicine Committee, said:

“These data only relate to the Pfizer-BioNTech vaccine, and to England, where we have also been using the Oxford-AstraZeneca vaccine in England. The emergency use authorisation came through later, for the latter, however, which might explain why this early data relates only to the Pfizer-BioNTech vaccine.

“We already have a considerable amount of data – not least from Israel – on this vaccine. These additional data from PHE confirm what we have already learned, allowing us to be more confident in the learning. Over time, as more data come in, we will be able to increasingly precise about the efficacy against different end-points (infection; mild-to-moderate disease; severe disease; hospital admission; death; and “long-Covid”).

“These data show that the vaccine reduces infection – based on routine testing of healthcare workers (HCWs), which would detect (subject to the approximate 70% sensitivity of the tests) infection in asymptomatic HCWs. This adds to the data on infection from the recent Lancet letter from Israel, showing a reduction in infection in HCWs; but, since we have been systematically testing HCWs in the UK (in contrast to in Israel, where it’s not clear how they detected asymptomatic infections), the UK data is more useful. It found that the risk of being infected was reduced by 70% after a single dose, and by 85% after a second dose.

“This is crucial, and extremely good news.

“If we are to achieve “herd immunity” through the vaccine programme, we need the vaccine to prevent infection and transmission. These early data from this and the Israel studies are the first to demonstrate real-world reductions in infection, which mean likely reductions in transmission.

“These data also show that, overall, hospitalisation and death will be reduced by 75% after a single dose of the vaccine. The efficacy in those over the age of 80 was not as good; this is not surprising, as it is generally the case that “immunosenescence” (age-related reduction in the immune system’s ability to respond to challenge, including vaccination) reduces vaccine efficacy in older people. In the over-80s the study found that:

• One dose is 57% effective against symptomatic COVID-19 disease.
• The second dose improves protection against symptomatic disease by a further 30%, to more than 85%.
• The risk of dying is less than half (56%) in vaccinated cases compared to unvaccinated cases, at least 14 days after receiving the first dose.
• Those over 80 who develop COVID-19 infection after vaccination are around 40% less likely to be hospitalised than someone with infection who has not been vaccinated (it is not clear to me if this is after the first dose and can be expected to be greater after two doses).

“The vaccine was also confirmed to be just as effective against the more infectious B.1.1.7 variant (sometimes referred to as the “Kent variant”).

“These findings are, of course, based on preliminary data. Continuing post-implementation surveillance will continue indefinitely and, over time, the precision of the estimates of efficacy will improve.”

‘PHE monitoring of the early impact and effectiveness of COVID-19 vaccination in England’ and ‘Effectiveness of BNT162b2 mRNA vaccine against infection and COVID-19 vaccine coverage in healthcare workers in England, multicentre prospective cohort study (the SIREN study)‘ from Public Health England was published at 15:30 UK time on Monday 22^nd December.

Declared interests

None received.