Covid Vaccines: The Good, The Bad, The Ugly

covid-vaccines:-the-good,-the-bad,-the-ugly

23-07-21 12:30:00, Israel: Pfizer vaccine effectiveness by outcome and time of vaccination (MOH/Segal)

Updated: July 30, 2021
Published: July 23, 2021
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The latest data from Israel and the UK on covid vaccine effectiveness.

The latest data from Israel, which has used primarily the Pfizer mRNA vaccine, indicates that vaccine effectiveness against Delta coronavirus infection and symptomatic (“mild”) disease has dropped from about 95% to about 40%, whereas effectiveness against hospitalization and severe disease (i.e. low blood oxygen levels) remains at 80% to 90% (see chart above).

Importantly, in people who got vaccinated already in January 2021 (primarily the elderly), protection against infection and mild disease may already have dropped to near 0% (see chart above). Moreover, since the Delta covid outbreak is still accelerating in Israel, the effectiveness against hospitalization and severe disease may further decrease (due to lags in hospitalizations).

(Update: New data from Hebrew University shows that protection against severe disease has already dropped to 80%; compared to the original 96%, this results in a five-fold increase in residual risk.)

In the UK, which has primarily used the AstraZeneca DNA adenovector vaccine, the latest estimate by researchers at University College London indicates an effectiveness against infection of about 20% and a total effectiveness against severe disease of about 60%. In very senior citizens, the effectiveness against severe disease may be even lower (due to a weaker immune response).

(A substantially higher estimate by Public Health England, recently published in the New England Journal of Medicine, was based on outdated data from early June. Interestingly, the British government hasn’t updated its data on AstraZeneca vaccine effectiveness since June 13. Update: New data from PHE confirms that effectiveness against infection has dropped below 20%.)

The Israeli data shown above indicates that effectiveness against infection and mild symptoms decreases rapidly over time and reaches near-zero levels after about half a year. Most likely, this is because covid vaccines do not achieve mucosal immunity (in contrast to natural infection) and serum antibody levels (i.e. antibodies in the blood) decrease within months (see chart below).

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