In premarket trading on Thursday, Johnson & Johnson stock climbed 0.3 % after a real-world study found that a booster of the drugmaker's single-dose COVID-19 vaccination was 84 % effective among preventing hospitalization in South African healthcare workers infected with Omicron.

According to the study, the J&J vaccine's effectiveness in preventing hospitalization increased from 63 % following a booster shot to 84 % 14 days later. At one to two months after the boost, effectiveness had reached 85 %.

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A study employing a homologous (identical vaccine) booster dose yielded the results. The findings have not been subjected to peer review.

A separate study used the J&J booster in patients who had previously been vaccinated with Pfizer BioNTech's two-dose BNT162b2 mRNA vaccine and found that they were protected against the mutant.

The J&J booster produced a 41-fold increase in neutralizing antibodies and a five-fold increase in immunity-enhancing T-cells against Omicron, according to the second investigation.

In the United States, J&J has behind Pfizer and Moderna in vaccinations, as only these three companies have been approved to advertise their vaccines in the country. In addition, it is the country's only single-dose vaccine.

The company wasn't considered as a huge benefit of the FDA's decision to allow boosters earlier this year – when Omicron wasn't quite the menace it had become – but with Omicron now blazing across the United States and the rest of the world, the findings could help it.

According to the New York Times, the number of new COVID cases in the United States reached 488,000 on Wednesday, a new high.