Scotland’s vaccine rollout suggests delaying the 2nd COVID-19 shot is a bad idea

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The UK’s strategy of delaying second coronavirus vaccine doses up to 12 weeks in order to give more people a first shot may carry serious risk.

On Monday, Scottish researchers released data from their vaccination campaign, including more than 1 million people who’ve been immunized, that suggests protection from a single dose peaks and then declines after about five weeks.

The Scottish data hasn’t been published in a medical journal or reviewed by independent scientists. The results were posted as a preprint on Monday.

The experiment used medical records covering 5.4 million people, or 99% of the Scottish population and focused on people who had received a single shot of either Pfizer’s or AstraZeneca’s vaccine, the only two shots authorized in the UK. One dose helped protect against hospitalization, with effectiveness peaking about five weeks after immunization at 84% effective at preventing hospitalization.

But the follow-up data available beyond that time is where it gets concerning. Effectiveness peaked and then began to decline, going from 84% effective in the fifth week to 61% effective the following week and then 58% beyond then.

It’s unknown if efficacy will keep dropping going forward, as that’s all the data the researchers had available to crunch in the study. But the findings suggest that protection starts to wane from a single dose after five weeks or so.

That could have major implications for the UK’s strategy, which delays people’s second doses out to 12 weeks after the first dose. The urgency of the pandemic combined with the scarcity of available doses has led public-health leaders around the globe to mull whether or not it’d be better to get a single dose in as many people as possible or to provide two doses on time to fewer people. 

Scotland, as part of the UK, is delaying second doses to get more first doses in arms and rolling out two vaccines developed by Pfizer/BioNTech and AstraZeneca/University of Oxford. Both were tested in clinical trials as two-dose regimens, respectively given 21 days and 28 days apart. 

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Vaccine experts say delaying 2nd dose ‘is a mistake’

Several vaccine experts said the data supports giving people the second dose at the right time, as studied in large-scale clinical trials. These studies, which tested vaccines against placebo injections, were the basis for authorizing the shots and are seen as the highest-quality evidence in medical research. 

“I think delaying the second dose for a considerable period of time is a mistake,” Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, told Insider. 

Dr. Kavita Patel, a primary-care physician who previously worked on healthcare policy in the Obama administration, also expressed concern about the data and what it suggests about delaying second doses. 

In an email to Insider, Patel called delaying the second dose “dangerous,” with the new Scottish data being “even more concerning.” 

Patel also said she worried the public debate about whether or not to delay the second dose could be sending a harmful, unintentional message to the public. As doctors …read more

Source:: Business Insider – Science

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