With delta variant circulating, L.A. County will need more than 80% vaccinated to reach herd immunity

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Juan Rodriguez, left, reacts while receiving Johnson & Johnson's Janssen COVID-19 vaccine administered by vocational nurse Christina Garibay at a Skid Row community outreach event in Los Angeles on Aug. 22, 2021. (Frederic J. Brown / AFP / Getty Images)

Juan Rodriguez, left, reacts while receiving Johnson & Johnson’s Janssen COVID-19 vaccine administered by vocational nurse Christina Garibay at a Skid Row community outreach event in Los Angeles on Aug. 22, 2021. (Frederic J. Brown / AFP / Getty Images)

With the highly contagious delta variant still predominant in Los Angeles County, public health officials say the region will no longer reach herd immunity against the coronavirus once 80% of eligible residents are vaccinated.  

Initially, public health Director Barbara Ferrer projected L.A. County could get 80% of those eligible vaccinated and reach herd immunity by late July. But that was in May, and dependent on vaccinations keeping up at the same rate.

The projected date was repeatedly pushed back as vaccinations lagged, and in June Ferrer said she didn’t expect the county could reach its goal before fall as the delta variant took hold in the region.

Now, the delta variant accounts for 99% of all cases sequenced in the county, and researchers are still trying to determine the effectiveness of each vaccine against the highly contagious variant.

“I think delta has scrambled everything, mostly because it’s so much more infectious,” Ferrer said in a briefing Thursday.

L.A. County is still short of even the 80% vaccination rate goal. Ferrer said currently 75% of residents 16 and over have at least one dose, and 65% of residents 12 and over are fully vaccinated.

Ferrer didn’t say what vaccination rate she thinks the county now needs to reach herd immunity, but she said there still aren’t enough people coming in each week to get a shot.

Current data shows a little over 63,000 doses were administered across the county from Aug. 16 to Aug. 22, though she noted that figure could rise anywhere from 4,000 to 10,000 doses due to reporting lags. Still, that wouldn’t be enough.

“In order to avoid the cycles of surges, we do need to see this number rise significantly if we’re to take a different path through the coming months,” Ferrer said.

County officials want to focus on reaching more Black residents under age 50 and Latinos younger than 16, both groups that have vaccination rates below 50%.

“It’s not a coincidence that the communities with the lowest vaccination uptake are the ones who have historically had the lowest access to high-quality, affirming, respectful medical care,” Ferrer said. “And while repairing the damage caused by structural racism will not happen overnight, we need to see faster gains to turn around the disproportionality in cases, hospitalizations and deaths.”

Health officials are continuing to operate mobile vaccination teams in an effort to reach underserved communities where people aren’t yet vaccinated.

The delta variant is more easily spread between people, “likely due to its faster replication, higher viral load and greater affinity for lower respiratory tract cells when compared with earlier COVID strains,” Ferrer said.

And while vaccines do offer protection from severe infection, even vaccinated people can become infected with the delta variant and spread it — making a high vaccination rate more important than ever to protect those who are ineligible for a vaccine.

Ferrer noted that even though the county’s test positivity rate is currently relatively low, its case numbers and rates remain relatively high. That means even though there’s less transmission in general, more people are getting infected because the delta variant can spread to more people at once.

Ferrer said her concern is that with a good amount of people remaining unvaccinated, there can be room for more transmission as well as the development of new, and potentially even more dangerous, mutations.

“Without enough people getting vaccinated very rapidly, we could get another cycle later on in the fall or early winter caused by even another variant,” she said. “We have to be super careful.”

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