According to the data released in Feburary, the Chinese vaccines provided protection against Delta and Omicron comparable to the mRNA ones. See my post
#17646 in this thread.
Shanghai just released a detailed breakdown of the 6 + 55 new cases reported on Mar 13, with the vaccination information of each case. But it does not say whether the "fully vaccined" cases took the booster shot or not.
Out of the 6 symptomatic cases, 1 male of 78 yo is not vaccined. This patient, and another male of 58 yo, were asymptomatic then turned symptomatic.
In the 55 asymptomatic cases, I counted 10 of them did not have full vaccination, including 3 kids below 10 yo.
"On this day til 5pm, Shanghai health authority has tested and traced 8985 persons who could have had 'immediate contacts' (密接) with an infected person, and 27548 persons who could have had 'close contacts' (次密接). So far, 8520 of the 8985 immediate contacts cases are negative, 27322 of the 27548 close contacts cases are negative, with the rest still under investigation."
I don't remember having seen 次密接 before. If it is indeed a new category, Shanghai is refining the process.
In the past 4 to 5 days, Shanghai has had confirmed cases, symptomatic or not, reported all over the place, it is safe to assume that the spread has been going on for longer. Even with the median incubation period of 5 to 6 days (Omicron is said to have shorter incubation period), we should have seen the curve rising up quickly. But it is not the case for Shanghai. The curve has been flat. The total cases reported have been almost constant, between 50 and 100, for each day.
One possible explanation would be that the vaccines have protected most of whom were exposed from being infected.
Another possibility would be that there are still large number of infected persons not counted by the health authority because it has not done enough PCR tests and contact tracing. Such uncounted cases are likely without any symptoms to be notified.
Or it could be a bit of both.
We will see in a few days.
