On Friday, the Food and Drug Administration approved a new vaccine from GlaxoSmithKline to prevent shingles in adults age 50 and older, but not chicken pox. The two diseases may arise from the same virus, but they afflict different populations and that is key: The immune systems of the elderly susceptible to shingles are different from the immune systems of children susceptible to chicken pox.
GlaxoSmithKline’s shingles vaccine contains a lone protein isolated from the shell of the varicella zoster virus. This protein acts as an ID tag, allowing the immune system to recognize all future varicella zoster viruses it encounters.
On the other hand, the existing chicken-pox vaccine, aimed at children, contains a whole, live, but weakened varicella zoster virus. “Live viral vaccines tend to work better in children,” says Ann Arvin, an infectious-disease specialist at Stanford University. (Arvin has consulted for both GlaxoSmithKline and Merck, which makes the chicken-pox vaccine.) The reasons are not entirely well understood, but children have a different mix of immune cells than adults, and live viruses tend to provide better, broader immunity through life.
But live viruses, even weakened in a vaccine, can pose problems for people whose immune systems are weak due to age or disease. Such vaccines could make them sick. There is an existing shingles vaccine, made by Merck—basically a super-large dose of its live chicken-pox vaccine—but it is not recommended for immunocompromised patients.
It also works less well than GlaxoSmithKline’s new vaccine, which is more than 90 percent effective. “It’s a real paradigm shift because there are no vaccines that perform so extraordinarily well for people in their 70s and their 80s,” says Rafael Harpaz, an infectious-disease specialist at the Centers for Disease Control and Prevention. Scientists attribute its stunning effectiveness to a new adjuvant, an additional chemical in the vaccine that primes the immune system for the viral protein. A CDC panel on Wednesday actually voted to recommend GlaxoSmithKline’s new shingles vaccine even for people who had received Merck’s old shingles vaccine.
But could GlaxoSmithKline’s shingles vaccine work to prevent chicken pox as well? “We don’t know that, and I’m not sure if we ever will,” says Anne Gershon, a pediatric-disease specialist at Columbia University. (Gershon has received research funding from Merck and consulted for GlaxoSmithKline.) We might never know because someone would have to test it—and given that a safe, effective chicken-pox vaccine already exists, it’s unlikely anyone will ever take the risk. A GlaxoSmithKline spokesperson confirmed the company has no plans to test its vaccine for chicken pox.
Conversely, the chicken-pox vaccine does seem to offer some protection against later occurrences of shingles. The weakened varicella zoster virus strain in vaccines also lurks dormant in neurons, but it does not reawaken so easily. Kids who got chicken-pox vaccines are less likely to later get shingles than kids who naturally caught chicken pox.