Why are vaccinated people still getting COVID-19 infections?

Answers to your questions about ‘breakthrough’ cases of the virus

Masks are being recommended once again to stop the spread of COVID-19, this time even for fully vaccinated people when they are indoors in areas where infection rates are surging. The recommendation comes amid a growing number of cases where people who are fully vaccinated develop symptomatic illness. Here’s what public health experts say about those breakthrough cases.

Why aren’t the vaccines preventing breakthrough cases?

No vaccine is 100% effective at preventing COVID-19 infection, though the Pfizer/BioNTech and the Moderna vaccines are about 95% effective with the original strain of the virus. With the highly contagious delta variant, efficacy in preventing symptomatic disease is somewhat lower, at about 88% for those who received both doses of the Pfizer shots, according to preliminary studies. The two-dose Moderna vaccine is believed to offer similar efficacy.

The one-shot Johnson & Johnson vaccine is about 72% effective at preventing infection with the original virus. A J&J report released in July indicated that its vaccine has only a small drop in efficacy against the delta variant, though a recent independent study showed a more significant drop.

Are most of the breakthrough cases related to the delta variant?

Apparently. With the highly contagious delta variant now accounting for the vast majority of sequenced COVID-19 cases in the U.S., breakthrough cases have been on the rise. That may be because the variant has a much higher viral load, according to recent research.

How many breakthrough cases have resulted in patients being hospitalized or dying?

While the number of breakthrough cases are higher than had been anticipated, serious cases so far appear to be rare. As of July 19, among the 163 million U.S. residents who are fully vaccinated, the Centers for Disease Control and Prevention has received reports of 5,914 patients with breakthrough cases resulting in hospitalization or death. The CDC notes, however, that the numbers are likely an undercount because reporting is voluntary.

In Georgia, preliminary data indicate that 4,980 fully vaccinated residents have tested positive for the coronavirus, but among them only 118 have been hospitalized, and 24 have died due to COVID-19, according to the Department of Public Health.

Who is most vulnerable to serious illness from breakthrough infections?

Of the 5,914 patients nationwide with serious breakthrough cases, 74% were in people age 65 or older, CDC reports. There were 1,141 deaths, though 292 of those were reported as asymptomatic or not related to COVID-19, according to the agency.

If the risk of serious disease is so rare, why the heightened concern?

One reason is the risk of transmission. Even though the fully vaccinated people are likely to have only mild cases, there is evidence that they can have about the same viral load in their nose and throat as infected unvaccinated people, CDC Director Dr. Rochelle Walensky said recently. That means vaccinated people, including those with no symptoms, could spread the virus to others, including children under age 12 for whom no vaccine has been authorized.

Another concern is whether people with mild breakthrough cases may develop “long” COVID, where symptoms last for months. Recently, Dr. Anthony Fauci, who advises the White House on COVID-19 policies, said that is now being studied, but he didn’t know if that was a risk.

Who is tracking the breakthrough cases?

State health departments voluntarily report them to CDC. It then investigates those cases where fully vaccinated people were hospitalized or died.

What is CDC looking for?

It is monitoring for clustering by patient age, locations, underlying medical conditions, type of vaccine received and whether a specific coronavirus variant caused the infection.

Where are the risks highest in Georgia?

Public health authorities say that most of the new COVID-19 cases have been in areas with low vaccination rates. In Georgia, 40% of all residents are fully vaccinated. The counties with the highest vaccination rates are Fayette, Oconee, Cobb, Fulton, Forsyth, Greene, Clayton and Gwinnett, according to data from the Georgia Department of Public Health. Their rates are 45% or higher. The counties with the lowest rates are Long, Charlton, Chattahoochee, Brantley and Wheeler, all with rates under 20%.

In the last two weeks, Chattahoochee County has had the highest rate of new cases in Georgia, followed by neighboring Stewart County. Two counties in the Southeast corner of Georgia, Camden and Charlton, also have high rates of newly confirmed cases. COVID-19 cases are soaring in nearby Jacksonville, Fla., which has reported having more patients hospitalized than during the worst point in January.

Staff writer Helena Oliviero contributed to this article.