Shingles is caused by the same virus that causes chickenpox and typically presents itself as a painful, itchy rash that develops on one side of the body.
Viral infections like shingles are particularly prevalent in people who have undergone stem cell transplants given their typically weaker immune systems.
Shingrix - which is a two-dose vaccine and costs around US$280 - has been approved in the US and Canada for otherwise healthy over-50s, but GSK thinks it can reduce the risk of getting shingles in other patient populations too.
The ZOE-HSCT phase III study tested the vaccine on adults over the age of 18 who had just undergone autologous haematopoietic stem cell transplant (auHSCT).
It succeeded in its primary objective, demonstrating that Shingrix reduced the chances of getting the virus by 68% in over-18s and by a similar percentage in over-50s.
The vaccine reduced overall complications linked to shingles by almost 78% and no safety issues were detected during the trials.
GSK said it is evaluating these results together with those of other phase III studies in immune-compromised patient populations.
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"The immune systems of these stem cell transplant recipients is substantially weakened compared to the general older adult populations studied in other Shingrix efficacy trials," Emmanuel Hanon, Senior Vice President and Head of Vaccines R&D for GSK said.
"This puts them at much higher risk for viral diseases like shingles and, at the same time, makes developing an effective vaccine to help protect them more challenging."
"Today's results, demonstrating the vaccine's ability to help prevent shingles and its complications with just two doses, may provide a much-needed benefit to these patients considering the high incidence and burden of disease they face," he said.
GSK shares were down 0.5% to £12.72 early on Wednesday.