Single Covid vaccine dose in Israel 'less effective than we thought'

https://www.theguardian.com/world/2021/jan/19/single-covid-vaccine-dose-in-israel-less-effective-than-we-hoped

Israel’s coronavirus tsar has warned that a single dose of the Pfizer/BioNTech vaccine may be providing less protection than originally hoped, as the country reported a record 10,000 new Covid infections on Monday.

In remarks reported by Army Radio, Nachman Ash said a single dose appeared “less effective than we had thought”, and also lower than Pfizer had suggested.

By contrast, those who had received their second dose of the Pfizer vaccine had a six- to 12-fold increase in antibodies, according to data released by Sheba Medical Center in Tel Hashomer on Monday.

The issue of some vaccines being less effective after a single dose rather than two is well known, as well as the fact that protection is not immediate. While the first dose can take several weeks to promote an effective antibody response, the second dose can trigger different responses, supercharging the protection. Pfizer itself says a single dose of its vaccine is about 52% effective. Some countries such as the UK have delayed administering their second doses to try to maximise the number of people given a first dose.

Questions over the effectiveness of the vaccine were raised amid reports that thousands of Israelis were still becoming sick after receiving the vaccine, although the public health services head, Sharon Alroy-Preis, said that in most cases this was because the individuals had not built up sufficient antibodies after being inoculated before being exposed to the virus.

The latest figures for Israel, which has implemented one of the fastest national vaccine efforts, underscore the huge challenges still being faced around the globe even in countries with aggressive coronavirus vaccine programmes.

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