Pfizer Covid-19 vaccine provides - no protection in first 8 days, perhaps even makes patient more easy to infect, - days 9 to 14 protection begins improving at a fast rate -days 15 to 21 protection further improves to over 90% the above comes from a British study of how the Pfizer vaccine performed on Israeli citizens.
The research team set out to estimate the effectiveness of the Pfizer vaccine after a single dose—by reanalysing real-world outcomes from Israel.
They used the data to see how the Israeli vaccination programme impacted case numbers, and went on to estimate vaccine effectiveness over time.
They found that after the initial vaccination—case numbers increased for eight days before declining to low levels by day 21.
Prof Hunter said: "Surprisingly, the daily incidence of cases increased strongly after vaccination till about day eight—approximately doubling. We don't know why there was this initial surge in infection risk but it may be related to people being less cautious about maintaining protective behaviours as soon as they have the injection.
"We found that the vaccine effectiveness was still pretty much zero until about 14 days after people were vaccinated. But then after day 14 immunity rose gradually day by day to about 90 percent at day 21 and then didn't improve any further. All the observed improvement was before any second injection.
"This shows that a single dose of vaccine is highly protective, although it can take up to 21 days to achieve this.
"And it supports the UK policy of extending the gap between doses by showing that a single dose can give a high level of protection.
