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Expect more 'breakthrough' coronavirus cases among the vaccinated, Metro Health says

So far, about 1 percent of vaccinated Bexar County residents have caught the virus despite the inoculation. The public health authority says that share will grow.

SAN ANTONIO — San Antonio's public health authority says more vaccinated residents are contracting the coronavirus, and top doctors expect a rise in these so-called 'breakthrough' cases. 

Metro Health assistant director Dr. Anita Kurian says roughly one percent of fully-vaccinated San Antonio residents have contracted the virus. 

"As the pandemic lingers and we have more transmissible variants like the Delta variant circulating widely, we expect that number of breakthrough cases will rise," Kurian said. 

More than 30 fully vaccinated people who live in an assisted living facility on the city's northwest side were in quarantine after an outbreak of breakthrough cases there this week. Other unvaccinated staff-members contracted the virus, too. 

Vaccines are not 100 percent effective. Though they can prevent infection, vaccines are not designed primarily for that purpose.

"Our interest is in preventing severe infections, hospitalizations, long-term consequences, and death," WellMed COVID-19 Vaccine director Dr. Michael Almaleh said. "These vaccines do a very, very good job at preventing all of those serious outcomes." 

Almaleh says it's not yet clear which groups of vaccinated people are most likely to suffer a breakthrough case. Older people or those with weakened immune systems are most likely to be hospitalized because of breakthrough infections, according to CDC data.

"It would be safe to assume that people with weakened immune status, people who are older, and people who live in spots with low vaccination coverage have a greater likelihood of a breakthrough infection," Kurian said. 

Though not solely responsible, Kurian says the Delta variant will contribute to an increase in breakthrough infections.

The Delta variant accounts for 78 percent of Bexar County coronavirus samples sent off for genomic sequencing. This does not mean the variant is responsible for 78 percent of all community spread in San Antonio, since not all samples are sequenced. 

The Delta mutation is especially good at slipping past the body's defenses, attacking cells from angles they are not as prepared to defend. Still, vaccines are nearly 90% effective at stifling Delta variant infections.  

"Vaccinations are critical, even if vaccinations are not 100 percent effective," she said. "Infection doesn't equate to disease, right? You may test positive, but not necessarily become severely ill with the virus."

Since February, 99.5 percent of Texans who've died from Coronavirus complications had not taken the vaccine. The state says just 43 people have died from breakthrough infections. 

"It's pretty clear at this point that those individuals that are having breakthrough infections are having much more mild cases or are asymptomatic," Almaleh said.