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More evidence it’s okay to delay second dose of COVID vaccines

This time from peer-reviewed AZ data and real-world data on Pfizer/BioNTech vaccine

This time from peer-reviewed AstraZeneca data and real-world findings from Pfizer/BioNTech vaccine.

Feb 20, 2021 | 3:18 AM GMT

New findings reported for COVID vaccines from partners Pfizer and BioNTech and AstraZeneca could better inform public health decisions on vaccine schedules by supporting the spacing out of first and second doses.

One study, reported Friday by Chaim Sheba Medical Centre and Tel Aviv University researchers in The Lancet, shows the efficacy of Comirnaty (BNT162b2) from Pfizer Inc. (NYSE:PFE) and BioNTech SE (NASDAQ:BNTX) rises quickly after the first dose. 

The second paper, also published in Lancet, demonstrated efficacy for a single dose of COVID-19 Vaccine AstraZeneca (AZD1222) from AstraZeneca plc (LSE:AZN; NASDAQ:AZN) and the University of Oxford, and showed that the efficacy rose with increasing intervals between the two doses.

The two studies support the idea that delaying booster shots for a few weeks won’t dramatically compromise protection from symptomatic disease.

The U.K. already allows flexible dosing schedules. MHRA authorized a two-dose regimen of the AstraZeneca vaccine with a 4-12 week interval, and the country’s Joint Committee on Vaccination and Immunization published a statement on Jan. 6 advising a maximum interval between the first and second doses of 12 weeks for both the Pfizer-BioNTech vaccine and COVID-19 Vaccine AstraZeneca.

Several other countries are taking the same view. 

FDA, by contrast, hasn’t yet budged on dosing schedules, despite calls from prominent figures including former FDA commissioner Scott Gottlieb and former Operation Warp Speed Chief Scientific Adviser Moncef Slaoui. 

In a statement released on Jan. 4, the agency said it wants to “remind the public about the importance of receiving COVID-19 vaccines according to how they’ve been authorized by the FDA” to achieve the level of protection in the clinical trials that supported their emergency use authorization.

New Comirnaty data

The new Comirnaty findings come from real-world data collected by Chaim Sheba Medical Centre showing the vaccine reduces symptomatic disease by 85% and all SARS-CoV-2 infections, including non-symptomatic cases, by 75% in the week before and the initial week after booster vaccination when immune responses are still building.

The findings came from a comparison of 7,214 healthcare workers at Chaim Sheba who received at least one dose of the vaccine by Jan. 24 to 1,895 unvaccinated healthcare workers. The data were adjusted to account for the probability of contact with an infected individual given the rates of infection in the community.

Comirnaty’s unadjusted efficacy on days 15-28 was 60% against any infection and 75% against symptomatic COVID-19.

The 15-28 day timeframe corresponds to the weeks before and after the booster dose in clinical trials, which occurred at day 21.

Previously, Phase I data from the vaccine showed volunteers aged 18-55 years had their highest antibody titers around day 28, and pivotal testing showed protection started to emerge about 10 days after the first shot, meaning the 15-28 day timeframe corresponded to the window when vaccine-induced immune responses were building.

New AstraZeneca data

Also on Friday, a separate Lancet paper from the University of Oxford, which the journal initially released as preprint on Feb. 1., showed COVID-19 Vaccine AstraZeneca was more protective with increased time between prime and booster doses.

The paper also showed that the vaccine’s single-dose efficacy against symptomatic disease was 76% on days 22-90. It fell to 32% on days 90-120, indicating a need for a second dose.

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