UK health officials have decided to delay giving second doses of Covid-19 vaccines and even permit combining doses from different manufacturers, prompting international concern. Why has the UK decided to lengthen the gap between the first and second doses of vaccine? The original plan was to offer priority groups an initial shot of vaccine, followed by a second dose three weeks later. This second “booster” dose is likely to strengthen and optimise the duration of the immune response, resulting in longer-term protection. Neither has giving a first dose of the Pfizer/BioNTech vaccine, followed by a second dose of the Oxford/AstraZeneca vaccine, or vice versa – which the JCVI advises only in “exceptional circumstances”, eg if a second dose of the original vaccine isn’t available.

Source: The Guardian January 06, 2021 17:28 UTC