GlaxoSmithKline (GSK) has reported positive results from Phase I/II clinical trials of Respiratory Syncytial Virus (RSV) vaccine candidates for maternal immunisation and older adults.

Data showed that the two FDA fast-tracked candidate vaccines trigger robust immune response and are well-tolerated.

RSV is a major cause of respiratory infections, such as bronchiolitis and pneumonia, in infants and older adults.

Both RSV vaccines are made of recombinant subunit pre-fusion RSV antigen (RSVPreF3) that can potentially trigger the required immune response.

The vaccine for older adults also includes GSK’s AS01 adjuvant system to boost the immune response since this group tends to show a weaker immune response to vaccination as compared to younger adults.

Initially, the vaccine candidate for older adults was tested in 48 healthy participants aged between 18 and 40 and then in 1,005 healthy adults aged between 60 and 80. Either different dosages of antigen plus adjuvant or placebo was administered.

Interim data obtained after a month of immunisation showed that the candidate vaccine elicited a humoral and cellular immunity compared with baseline.

A ten fold increase in protective antibodies was also noted in immunised participants.

Importantly, the cellular immunity of the vaccinated older adults was boosted to reach range to that observed in the younger adults after vaccination with the non-adjuvanted formulation.

In 502 healthy non-pregnant women, the maternal RSV vaccine was tested with three different doses over monthly visits at day eight, 31 and 91, post-immunisation.

According to the results, the vaccine was able to rapidly boost the pre-existing immunity at all dose levels as compared to the baseline.

A 14-fold increase in RSV-A and RSV-B neutralising antibodies titers was also observed at day eight.

GlaxoSmithKline senior vice-president and Vaccines R&D head Emmanuel Hanon said: “We are delighted to see these positive results confirming our approach to develop dedicated vaccines building on the strategic use of our platform technologies for the populations most at risk from RSV infections – young infants and older adults.”

GSK plans to progress these assets to Phase III trials to analyse their potential efficacy in the coming months.