Johnson & Johnson COVID-19 vaccine may not perform as well against Delta variant, says study

JNJ says data from study 'do not speak to the full nature of immune protection'.

The one-shot coronavirus vaccine from Johnson & Johnson is much less effective against the Delta variant than it is against the original version of COVID-19, according to a new study posted online Tuesday.

The study, which examined blood samples in a laboratory setting and has not yet been peer-reviewed, suggests that anyone who received the J&J $(JNJ)$ vaccine may need to receive a second shot as the variant continues to spread across the US.

"The message that we wanted to give was not that people shouldn't get the J&J vaccine, but we hope that in the future, it will be boosted with either another dose of J&J or a boost with Pfizer or Moderna," study leader Nathaniel Landau, a virologist at NYU's Grossman School of Medicine, told The New York Times .

Earlier this month, New Jersey-based Johnson & Johnson published preliminary data indicating its vaccine was effective against the Delta variant, first located in India, at least eight months after inoculation.

However, in May, the British government released a study vaccine, which is similar in structure to the Johnson & Johnson vaccine, was just 33 percent effective against "symptomatic disease" caused by the Delta variant, while two doses were 60 percent effective against symptomatic disease.

J&J spokesperson Seema Kumar told the Times that the data from the latest study "do not speak to the full nature of immune protection."

Last month, Centers for Disease Control and Prevention $(CDC)$ Director Dr. Rochelle Walensky told NBC's "Today" show that "we have every reason to believe ... that the J&J will perform well against the Delta variant, as it has so far against other variants circulating in the United States."

Walensky told lawmakers earlier Tuesday that the Delta variant currently accounts for 83 percent of all COVID-19 cases in the US. During the same hearing, White House chief medical adviser Dr. Anthony Fauci said researchers were still assessing whether booster shots would be needed to provide additional protection.

"We don't want people to believe that when you're talking about boosters, that means the vaccines aren't effective," Fauci said. "They are highly effective, we are talking about the durability of that."

Initial studies indicate that mRNA vaccines manufactured by Moderna $(MRNA)$ and Pfizer $(PFE)$ BioNTech $(BNTX)$ are effective against the Delta variant and could provide protection for years, provided the virus doesn't mutate far beyond its initial form.

The Delta variant has been blamed for an increase in cases, hospitalizations and deaths in recent weeks, though the numbers in all categories are still well below the peak of last winter's surge and the overwhelming majority of hospitalizations and deaths are occurring among unvaccinated people.

Despite that, health officials in Los Angeles and Las Vegas have reimposed mask mandates in indoor spaces, regardless of individuals' vaccination status.