The US National Institutes of Health (NIH) has found that the booster dose of Moderna’s Covid-19 vaccine, mRNA-1273, substantially improved neutralising antibody levels against all known SARS-CoV-2 variants of concern in a study in rhesus macaques.

The booster shot was administered nearly six months following the primary vaccine regimen.

According to the findings, enhanced neutralising antibody responses were maintained for a minimum of eight weeks after giving the booster shot and were found to exceed the levels higher than those achieved after the initial series.

Furthermore, the booster offered greater protection, signifying the ability to reduce viral replication in the lungs and nose.

The researchers also noted that the booster dose induces a robust immune memory response and possibly a durable immunity.

The mRNA-1273 vaccine that targets the original virus and another updated vaccine that acts on the Beta variant were analysed in the study with both of them demonstrating comparable ability to increase antibody responses and offer protection.

The study was conducted six months ago during the prevalence of the Beta variant of the virus, which had shown the capacity to resist neutralisation leading to reduced vaccine efficiency.

According to the researchers, the booster in humans could increase the duration and effectiveness of protection against upper and lower airway infection caused by any of the circulating variants of the SARS-CoV-2 virus, including Delta.

The team emphasised that these properties are vital to preserving protection against severe Covid-19 and potentially reducing mild infection and viral spread.

Furthermore, the findings back boosting among the elderly individuals, those with pre-existing health problems, greater exposure risk and those who did not respond well to the initial vaccine series.

Earlier, NIH found that interferon beta-1a plus remdesivir did not boost outcomes in an ACTT-3 trial conducted in hospitalised adult Covid-19 pneumonia patients.