As news arrives about the CDC telling people they don't need masks on in most outdoor settings if they're vaccinated, we get other news that California has recorded 1,379 cases of COVID among people who are considered fully vaccinated, underscoring the need for ongoing caution.

The numbers are not high and not a surprise — with the Pfizer and Moderna vaccines both considered about 90% effective two weeks after the second dose, that means 10% of the population who receives them is still vulnerable to infection. Add to that the approximately 25% still vulnerable among those with the J&J vaccine, and any other factors like alcohol consumption that may weaken a person's immune response to a vaccine, and you're going to still see some people infected.

We don't yet have data on how many people in California became seriously ill from these "breakthrough" infections — and a previous "real-world" study among vaccinated healthcare workers that began in December found no cases of serious illness, even if people tested positive. But as the Chronicle reports, between January 1 and April 21, nearly 1,400 tested positive more than 14 days after their second dose of a vaccine, or one-dose J&J vaccine. That's a mere 0.1% of the 1.4 million total cases reported in the state during that same timeframe, and reflects a similar national trend. Across the country, 5,800 "breakthrough" infections have been found since vaccinations began, according to the CDC.

Different Bay Area counties have been reporting these "breakthrough" infections, with the latest being Contra Costa County, where 128 cases have been found since January. Of those, as KRON4 reports, four required hospitalization. One death did occur among the group, but it was a case of an elderly person already in hospice care before the infection occurred.

That is 128 people out of 437,000 fully vaccinated residents to date, and more than 1 million vaccine doses that have been administered in the county. The county has a goal of fully vaccinating 1 million residents by the end of May.

As of today, nearly one-third of the state has received at least one vaccine shot, and in San Francisco, the number is 70%.

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