Data from new analyses were released Monday shedding light on the short-term impacts of COVID-19 vaccinations in the UK. One analysis from Public Health England's (PHE) SIREN study appears to corroborate early evidence that Pfizer and BioNTech's vaccine BNT162b2 offers high levels of protection against infection and symptomatic disease from the first dose, while another conducted by Public Health Scotland (PHS) indicates that COVID-19 vaccinations have lowered the risk of serious disease by cutting hospital admittance rates. Neither is peer-reviewed and both were released as preprints by The Lancet.
The SIREN study focused on staff working in NHS hospitals in the UK, and by the December 7 start date, there were 23,324 participants for the England cohort included in the analysis. At least one dose of vaccine was administered to 89% of participants by February 5, with 94% given BNT162b2, while 6% received AstraZeneca's AZD1222. Most of the cohort received at least one dose, while under 10% had received two doses.
Results, which focused on Pfizer's vaccine, demonstrated that BNT162b2 was 72% effective at reducing the risk of symptomatic and asymptomatic infection 21 days after the first dose, rising to 86% seven days after the second in the antibody-negative cohort. Overall, hospitalisation and death from COVID-19 declined by over 75% in those who received a dose of the vaccine.
Moreover, PHE's analysis of routine testing data also shows that one dose is 57% effective against symptomatic COVID-19 in people aged over 80, with the benefit seen from about three to four weeks after the first dose. Early data also suggest the second dose in over-80s improves protection against symptomatic disease to more than 85%. Meanwhile, PHE said that over-80s who develop COVID-19 infection after vaccination are around 40% less likely to be hospitalised than non-vaccinated individuals.
The agency noted that these levels of protection were also seen against the B.1.1.7 variant, which was predominant throughout the study period. Mary Ramsay, PHE's head of immunisation, said the data provide "strong evidence that the Pfizer and BioNTech vaccine is stopping people from getting infected, while also protecting cases against hospitalisation and death…We should be very encouraged by these initial findings."
The results came as new data were released Monday on COVID-19 hospital admissions in Scotland, showing there has been a "substantial reduction" in the risk of hospitalisations following a single dose of a coronavirus vaccine. Jim McMenamin, national COVID-19 incident director at PHS, said the findings "are important as we move from expectation to firm evidence of benefit from vaccines."
The analysis stems from the EAVE II project, which uses patient data from 5.4 million people in Scotland to track the COVID-19 pandemic and vaccine roll out in real-time. PHS and scientists at various Scottish universities looked at data on people who had received either BNT162b2 or AZD1222. The data were gathered between December 8 and February 15, a period during which about 1.14 million doses were administered and 21% of the Scottish population had received their first injection, according to PHS. Specifically, some 650,000 people had received the Pfizer and BioNTech vaccine, while about 490,000 had been immunised with AstraZeneca's product.
The early analysis found that there were just over 8000 people who were admitted to hospital, but only 58 were among the vaccinated group after the four-week mark. Compared to those who had not been vaccinated, people given BNT162b2 had an 85% lower risk of hospitalisation from COVID-19 by week four after the initial dose, while those who received AZD1222 saw their risk decline by 94%. Among those aged 80 years and over, vaccination was associated with an 81% reduction in hospitalisation risk in the fourth week when the results for both vaccines were combined.
Lead researcher Aziz Sheikh, director of the University of Edinburgh's Usher Institute, said "we now have national evidence – across an entire country – that vaccination provides protection against COVID-19 hospitalisations," and called for "rollout of the first vaccine dose…to be accelerated globally."
The UK had already adopted a policy of delaying the second dose of both vaccines by up to three months in a bid to vaccinate as many people as possible, a controversial move that led some to question whether the approach would give sufficient immunity. Pivotal studies of the Pfizer and BioNTech vaccine had involved a second dose being given after only three weeks, whereas trials of the AstraZeneca vaccine looked at a longer dosing interval. A recent pooled analysis of these indicated that giving two full doses of AZD1222 at least 12 weeks apart conferred 82.4% protection, compared with 54.9% when they were spaced within a shorter six-week gap.
The latest findings constitute the first evidence of the real-world impact of vaccination against SARS-CoV-2 in the UK. Data from a real-world analysis released last week of healthcare workers in Israel showed one dose of Pfizer and BioNTech's vaccine was 85% effective at preventing symptomatic disease 15 to 28 days after administration, and 75% effective at preventing both symptomatic and asymptomatic infections.
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