Could Houston-area reach herd immunity by late summer?

HOUSTON, Texas (KTRK) -- At large vaccination sites, like the one in Galveston County where staff is administering up to 5,000 vaccinations a day, the hard work is paying off.

Galveston County is actually one of the leading counties when it comes to vaccinations in the Houston area.

"We've actually gone to an open schedule system," said the county's health authority Dr. Philip Keiser. "We don't have a waitlist anymore because we found that as soon as someone got on the waitlist, we were actually giving them vaccines."

Eyewitness News looked at how many people have received at least one dose of the COVID-19 across the southeast Texas region. According to state data, in Montgomery County, it's at least 27% of the population.

In Brazoria County, 35% of the population has received their first dose, Harris County is at 36%, Galveston County is at nearly 40% and Fort Bend County is at 42%. With lagging data, Galveston County thinks their number could be closer to 50%.

So how many people need to be vaccinated before the region reaches herd immunity?

Experts say somewhere around 75% to 80%.

"What that would mean is the likelihood of COVID to be able to spread through a community wouldn't exist because most of the people are already immune to it," said Dr. James McCarthy, a chief physician executive at Memorial Hermann. "So we have this with many other diseases ... with measles, with flu, with polio."

McCarthy said there are two ways we can reach herd immunity.

"It will come from the people who've been vaccinated. It will also come from the people who have been exposed to COVID and developed their own antibodies," he said.

But if you had a mild infection, that immunity doesn't last long, according Houston Health Authority Dr. David Persse.

"We already know that with natural immunity from infection that there's a measurable decrease at about three months," he said.

Persse said he feels encouraged by the number of people getting vaccinated. He thinks at this rate, we could reach herd immunity by late summer or early fall, but for that to happen, people need to get the vaccine.

"My fear is that as things continue to improve, people will think, 'Well, I guess I don't need it now,' and that would be a mistake. That would be unfortunate because we'll never get to the level where we can really squash this virus, and it will continue to simmer through the community."

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