Thread by @joshmich

30% of Israel's population has received at least 1 dose of Covid-19 vaccine, but no indications yet that case numbers are coming down there (chart).

A few reasons why this might be:

1) Cases reported now were infected 7+ days ago, when vaccinations were lower

2) Less than 500,000 (out of ~2.7 M vaccinated) have so far received a 2nd dose. A single dose is "less effective than we hoped" in providing protection, according to Israeli health leaders.
theguardian.com/world/2021/jan…

3) Israel has vaccinated by age, starting with older persons, vaccinating to date:
80% of 70+
68% of 60-69
50% of 50-59
28% 40-49

Older ages are protected from severe disease, but younger ages typically contribute most to transmission
timesofisrael.com/israelis-aged-…

Officials are also "not certain the vaccine can protect against mutated variants of the coronavirus" though this appears to be speculation, with no direct evidence of vaccine compromise with variants circulating in Israel.
timesofisrael.com/israels-virus-…

Finally, we don't know exactly what fraction of the population must be immunized for transmission to be reduced (ie closing in on 'herd immunity'), but likely that Israel hasn't yet reached that level, even with 30% vaccinated.

Also, as has been a topic of discussion in recent days, prevention of disease in an individual is not the same as prevention of transmission. We hope there is a significant reduction in transmission from these vaccines but don't know for sure!