Pfizer/BioNTech COVID-19 vaccine offers ‘clear protection from first dose’, according to UK data
Public Health England (PHE) has published the first independent analysis of real-world data from COVID-19 vaccination in the country: finding the Pfizer/BioNTech vaccine provides ‘high levels’ of protection against infection and symptomatic disease from the first dose; as well as suggesting the vaccine may help interrupt transmission.
The first dose reduces the risk of catching infection by more than 70%; while one dose is 57% effective against symptomatic COVID-19 disease in those aged 80+ after 3-4 weeks from administration. Vaccination also appears to offer high levels of protection against the UK variant B.1.1.7.; with this strain in strong circulation over the period data was collected.
PHE is also monitoring the real-world impact of the AstraZeneca vaccine. It has not yet published these findings but says early signs are that the vaccine provides ‘good levels of protection from the first dose.’
The UK was the first to authorized the Pfizer/BioNTech vaccine, BNT162b2, and started its vaccination campaign on December 8. (The AstraZeneca vaccine was added to the program on January 4, and so there is not yet enough data available for this vaccine).
PHE’s SIREN study – which has yet to be peer-reviewed - followed more than 23,000 healthcare workers aged under 65 (data gathered up to February 8). These workers are tested for COVID-19 every two weeks regardless of symptoms.
Meanwhile, routine testing data has been looking at wider age groups: in particular over 80s, who accounted for a small proportion of phase 3 trials and thus had gathered limited data; but have since been the priority of the UK’s first tranche of vaccinations.
Looking at the impact of vaccination with the Pfizer/BioNTech vaccine, analysis of data finds:
- One dose reduces the risk of catching infection by more than 70% in health workers, rising to 85% after the second dose. “This suggests the vaccine may also help to interrupt virus transmission, as you cannot spread the virus if you do not have infection,” according to data from the SIREN study.
- One dose is 57% effective against symptomatic COVID-19 disease in those aged 80+, according to routine testing data. This occurs around three to four weeks after administration. Early data suggests the second dose in over 80s improves protection against symptomatic disease by a further 30%, to more than 85%.
- Vaccinated people who go on to become infected are ‘far less likely’ to die or be hospitalised. "Overall, hospitalisation and death from COVID-19 will be reduced by over 75% in those who have received a dose of the Pfizer-BioNTech vaccine."
- The risk of dying in those aged 80+ is less than half (56%) in vaccinated cases compared to unvaccinated cases, at least 14 days after receiving the first dose.
- Those aged 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.
The SIREN study also references studies from Israel – the country with the highest per capita level of vaccinations – which demonstrated vaccine effectiveness of 75% from 15-28 days following the first dose in reducing symptomatic infection.
Commenting on the English data, the UK's Health Secretary Matt Hancock said: "This crucial report shows vaccines are working – it is extremely encouraging to see evidence that the Pfizer vaccine offers a high degree of protection against coronavirus.
"It is important that we see as much evidence as possible on the vaccine’s impact on protection and on transmission, and we will continue to publish evidence as we gather it."
Scotland: 'First doses of vaccines led to substantial fall in hospital admissions
Meanwhile, a pre-print study published yesterday says the rollout of the Pfizer/BioNTech and Oxford/AstraZeneca vaccines in Scotland has led to 'a substantial fall in severe COVID-19 cases requiring hospital admission.'
The study - which covers both Pfizer and AstraZeneca vaccines - shows that the risk of hospitalisation from COVID-19 fell by up to 85% (Pfizer) and 94% (AZ) four weeks after vaccination of the first doses.
The researchers used a dataset that covers the entire Scottish population (5.4 million people) to compare outcomes for people in Scotland who had received their first dose of a covid-19 vaccine between 8 December and 15 February. During this period, 1.14 million vaccines were administered and 21% of the Scottish population received a first dose: 650 000 people received the Pfizer BioNTech vaccine and 490 000 the Oxford AstraZeneca vaccine.
Data defends second dose delay, says UK Government
The UK Government says the English data supports its policy of vaccinating as many people as possible with the first dose, even though this means lengthening the gap between doses (doses are being delivered 12 weeks apart as opposed to the 21 days in the Phase 3 studies and 6 week max advised by the WHO).
“The current dosing strategy will save more lives by ensuring more people receive protection from severe disease following the first dose,” the UK Government says.
“There is also good evidence suggesting that giving the second dose of AstraZeneca later will lead to much higher levels of protection. Offering the booster at 12 weeks will therefore help to ensure longer lasting protection beyond the current restrictions.”
The Scottish study, meanwhile, is based on the effect of one dose.
"To our knowledge, this is the first study of COVID-19 vaccine effect against hospitalisation for an entire nation after a single dose of vaccine," say the researchers in the study. "We found that a single dose of [Pfizer] BNT162b2 COVID-19 vaccine was associated with a vaccine effect (VE) of 85% (95% CI 76 to 91) for COVID-19 hospitalisation 28-34 days post-vaccination.
"A single dose of ChAdOx1 [AstraZeneca] vaccine was associated with a vaccine effect 94% (95% CI 73 to 99) at 28- 34 days post-vaccination.
"VEs increased over time with a peak at 28-34 days post-vaccination for both vaccines. Comparable VEs were seen in those aged ≥80 years for prevention of COVID-19 hospitalisation with a high combined VE of 81% (95% CI 65 to 90) at 28-34 days post-vaccination."
Researchers note the the data will reflect the fact that ages 80+ have been universally offered vaccination, whereas other age groups have not. In addition, the data on the AstraZeneca vaccine is much smaller; as is the data for people who have received two doses.
However, the authors note the primary interest is in the effect of one dose: given the policy interest in whether to defer a second dose to allow greater coverage of the general population. The researchers highlight the strength of their study through its size: collected through electronic health records data and national databases.
"We are likely to have excellent generalisability across the UK and potentially other countries with national programmes using these same vaccines," they say.
