DPH data reinforces vaccine efficacy against new Delta variant

The San Francisco Department of Public Health (SFDPH) released on July 30, 2021 new COVID-19 data showing a rapid rise in cases due to the highly infectious Delta variant, including breakthrough cases among vaccinated individuals. However, the data demonstrates that vaccines are proving highly effective in preventing not only illness, but also severe illness and hospitalizations.

San Francisco is averaging 176 new cases a day, a ten-fold increase since the beginning of June. New data released on case rates and hospitalizations show that case rates among the unvaccinated are more than double that of vaccinated individuals, and hospitalization rates among the unvaccinated are eight times higher. Unvaccinated people in the data presented include those who are not fully vaccinated.

“San Francisco’s response to COVID-19 has always been grounded in data, science and facts and the more data we can analyze to drive our public health decisions, the better,” said Dr. Grant Colfax, Director of Health. “The data we are seeing today shows vaccines are highly effective in protecting people from severe illness and hospitalizations due to COVID-19, even as we see some breakthrough cases. Getting vaccinated continues to be your best protection.”

The Delta variant is now the dominant strain in San Francisco, as is the case throughout the country, and is driving up cases and hospitalizations. San Francisco is one of the highest vaccinated cities in the world with 77% of the eligible population fully vaccinated, so breakthrough cases are expected.

The additional data will be updated weekly online along with the long provided daily data on confirmed cases, testing, and hospitalization across the San Francisco health care system.

Data highlights for San Francisco

• Vaccinated people are highly unlikely to be hospitalized due to COVID-19.
• The case rate among the unvaccinated population is more than double that of the vaccinated population in San Francisco.
• There have been no recorded COVID-related deaths amongst fully vaccinated people.
• San Francisco is averaging 176 new cases a day, a ten-fold increase since the beginning of June.

No vaccine offers 100% protection from infection, but all three authorized vaccines are effective at preventing serious disease. Based on clinical studies, breakthrough infections are to be expected but hospitalization due to COVID-19 are rare.

Testing positive for COVID-19 after being fully vaccinated does not mean the vaccine isn’t working, it just means that a person was exposed and the immune system responded. The vaccine’s job is to promote a healthy immune response. In other words, if you are fully vaccinated and contract the virus, your symptoms will most likely be mild, similar to the common cold.

Case data

The data on cases by vaccination status are estimates based on verifications of San Francisco case data matched to California Immunization Registry (CAIR2) vaccine data.

The 7-day rolling average among fully vaccinated individuals and not fully vaccinated individuals shows the trend in new cases. We calculate the rolling average by averaging the new cases for a particular day with the prior 6 days.

• 7-Day Rolling Average of Case Rate: 22.7 per 100,000
• 7-Day Rolling Average of Case Rate- Not Fully Vaccinated: 36.8
• 7-Day Rolling Average of Case Rate- Fully Vaccinated: 16.2

For reference, the highest our case rate reached during the third surge was 42.9 (January 8, 2021). The case rate in California overall is currently 14.2. San Francisco’s rate may register as higher than the state average because of the City’s robust testing and system of data tracking, including within heavily impacted communities. San Francisco currently conducts 500 tests per 100,000 residents compared to California’s rate of 360 tests per 100,000 residents.

Hospitalization data

COVID-19 hospitalization numbers are sourced from the California Hospital Association. The number of vaccinated patients hospitalized are obtained from matching the San Francisco COVID Hospital Data Repository (CHDR) to CAIR2 then validated through the DPH Task Force COVID Disease Response Unit. The vaccinated patients counted are those deemed to be hospitalized due to their COVID-19 diagnosis, not those hospitalized due to other causes who happen to test positive for COVID-19 before or during their stays.

Currently there are 86 COVID-19 patients in San Francisco hospitals of which 24 are in the ICU. This includes both residents and non-residents. The COVID-19 hospitalization census reached 256 during the third surge.

There have been 16 clinically validated fully vaccinated San Franciscans who have ever been hospitalized due to COVID-19. There have been 3,041 San Franciscans hospitalized for COVID-19 since the beginning of the pandemic. Fully vaccinated patients have accounted for just 0.5% of all COVID-19 hospitalizations in San Francisco.