Johnson & Johnson revealed Tuesday that, according to a recent study, a two-dose version of its  vaccine provides 94% protection against symptomatic infection, which makes a two-dose regimen of its vaccine comparable to a two-dose regimen of Moderna's or Pfizer's.

The company also said that adding a COVID-19 booster shot to its one-shot vaccination, similarly, provides increased protection against novel coronavirus.

While the one-dose Johnson & Johnson vaccine is reportedly 72% protective against the virus in the U.S., when a person receives a booster shot two months later, their protection is increased to 94%.

The company supported this announcement by providing details from three studies that analyzed various aspects of its Janssen vaccine.

Details from new studies

Johnson & Johnson said its ongoing Phase 2 trial of a two-dose regimen indicates that giving two doses 56 days apart provided 100% protection against severe COVID-19 and 94% protection against moderate to severe COVID-19 in the United States.

Globally, the two-dose regimen offered 75% protection against moderate-to-severe COVID-19.

A second study showed people given a booster shot six months or longer after their first dose had a 12-fold increase in antibodies in comparison with a four-fold increase for people who got a second dose at two months. This means protection should be stronger if people get boosters later.

Third, the company analyzed real-world data involving 390,000 people in the US. Using health insurance records through July -meaning this study included the time period when the Delta variant appeared in the U.S.- revealed that the one-shot J&J vaccine was 81% effective at preventing hospitalizations.

The pharmaceutical company said, "The Johnson & Johnson single-shot COVID-19 vaccine showed vaccine effectiveness against COVID-19-related hospitalizations at 86% for participants younger than 60 years, and 78% for those 60 years and older," 

"Among 390,517 vaccinated and 1,524,153 matched unvaccinated individuals, vaccine effectiveness 79% for COVID-19 and 81% for COVID-19-related hospitalizations," the Janssen-led research team wrote in a study posted online in a preprint.

"In high-Delta-incidence states, rates of observed COVID-19 were higher in both groups than in the national cohort," they added.

"In these states, vaccine effectiveness for observed COVID-19 was 79% overall and 78% during June and July, the months where Delta variant incidence was highest," they added.

The takeaway

Dr. Mathai Mammen, global head of Janssen Research & Development, said in a statement, "Our large real-world-evidence and Phase 3 studies confirm that the single-shot Johnson & Johnson vaccine provides strong and long-lasting protection against COVID-19-related hospitalizations." 

"Our single-shot vaccine generates strong immune responses and long-lasting immune memory. And, when a booster of the Johnson & Johnson COVID-19 vaccine is given, the strength of protection against COVID-19 further increases."

When to get the booster

Healthcare professionals recommend that, for outstanding protection against the virus, a person get the booster shot at any time between two months and eight months after being fully vaccinated. Some experts say the longer you wait, the better.

According to CNN, this is because the body mounts a variety of immune responses such as antibodies, which are immune system proteins that can either flag an invader or directly attack and neutralize it, and these build up quickly but wane over time.

The body also produces B cells and T cells, which contribute to longer-term protection. After a period of time, when B cells become less active, stimulating them with a boost can trigger them to respond by generating fresh antibodies more effectively.

After receiving emergency use authorization by the US Food and Drug Administration on February 27, Johnson & Johnson's single-dose vaccine has been given to about 14.8 million Americans, according to data from the US Centers for Disease Control and Prevention.