Second shot of Pfizer, Moderna vaccines necessary to protect against more contagious Delta COVID-19 variant, health officials say

Just one shot of Pfizer or Moderna vaccines only gives people 33% protection against Delta variant

SAN ANTONIO - – A plea is resounding from local health leaders in Bexar County when it comes to the new Delta COVID-19 variant and vaccines.

The variant, which now makes up 90% of the United Kingdom’s cases, is being blamed for much of India’s devastating COVID-19 crisis.

“This is a variant of COVID that is much more transmissible, so the usual things we do to take precautions don’t work as well,” Metro Health Medical Director Dr. Junda Woo said.

The variant now makes up about 10% of all U.S. cases, and while the Pfizer and Moderna vaccines work against it, they don’t hold up nearly as well if people only got one of the two doses required.

Woo said a new study found that having just one of the two doses only gives you 33% protection against the Delta variant. The two shots give you 88% protection.

“When I say the vaccines work, well, I mean that you can catch the virus and not get very sick,” Woo said.

As of June 14, 108,655 people in Bexar County only had their first doses completed, and to those people, Woo says it’s crucial to schedule that second dose now.

“It doesn’t matter if it’s been more than the recommended amount of time. You don’t have to restart the series. Just go ahead and get your second dose,” she said.

There are lots of places you can get that second dose. To find out the one closest and most convenient for you, visit and head to the vaccine section.


KSAT Q&A: Infectious disease Dr. Ruth Berggren discusses delta COVID-19 variant in Texas

About the Authors:

Courtney Friedman is a KSAT anchor and reporter. She has an ongoing series called Loving in Fear, confronting Bexar County’s domestic violence epidemic. She's also covered Hurricane Harvey, the shootings in Sutherland Springs and Santa Fe, and tornadoes throughout Texas. She’s a California native and proud Longhorn who loves calling SA home.

Misael started at KSAT-TV as a photojournalist in 1987.