Mass RZV vaccination may cut shingles burden in older adults in SG

Mass vaccination with a recombinant zoster vaccine (RZV) may decrease the burden of herpes zoster (HZ) or shingles in older adults in Singapore (SG), a study suggests.

“Shingles is a major public health concern in SG, given its rapidly ageing population … Without vaccination, the public health burden of shingles would be high,” said the researchers. “Shingles vaccination could reduce this burden.”

In the absence of HZ vaccination, an estimated 406,513 (27 percent) out of the total base case population of 1.51 million adults ≥50 years would have shingles, 68,264 (4.5 percent) would have post-herpetic neuralgia (PHN) or shingles-related long-term nerve pain, 54,949 (3.6 percent) would have other shingles-related complications (ie, ocular, neurological), and 17,762 (1.2 percent) would be hospitalized due to shingles.

With RZV, a total of 73,129 cases of HZ, 11,094 cases of PHN, 9,205 cases of other HZ-related complications, and 2,827 hospitalizations due to shingles would have been avoided. These numbers were 4–6 times higher than what could have been avoided with zoster vaccine live (ZVL; n=17,565, 2,781, 1,834, and 484, respectively). [Hum Vaccin Immunother 2024;20:2348839]

Of the five age-stratified cohorts (50–59, 60–64, 65–69, 70–79, and ≥80 years), RZV avoided the largest number of HZ, PHN, and other complications in the youngest cohort as opposed to no vaccination/ZVL (47, 39.3, and 41.1 percent, respectively).

“These results are reasonable considering the 50–59-year vaccinated cohort is overall the largest and is expected to have a greater number of life years remaining to benefit from an extended duration of protection through RZV,” the researchers explained. “[This finding suggests] that early HZ vaccination would result in the most substantial public health impact (PHI).”

The benefit of early vaccination is also supported by the number needed to vaccinate (NNV) results, as it showed that the NNV to prevent one case of HZ/PHN was lower for RZV (7/41) than for ZVL (26/163).

The study modelled the PHI of HZ vaccination in SG using the ZONA* model adapted with SG-specific key model inputs, where available. The base case analysis was conducted in adults ≥50 years, exploring three vaccination strategies (RZV, ZVL, no vaccination) under a mass vaccination setting (30-percent coverage).

Substantial public health burden

Shingles and its complications may have spillover effects on the patient’s family, caregivers, and society. [ScientificWorldJournal 2014;2014:749698] “Globally, the burden of HZ is substantial, with approximately one in three individuals expected to develop HZ in their lifetime. The risk of HZ grows with age, particularly from 50 years. For individuals who live to ≥85 years, the estimated lifetime risk of HZ increases from one in three to one in two,” the researchers explained.

In SG, the resident population is rapidly ageing as reflected by the fraction of individuals aged ≥50 years jumping to 38.3 percent in 2022 from 29.8 percent in 2011. [https://table builder.singstat.gov.sg/statistical-tables/downloadMultiple/ zX5lZdqFrk-29wjZN4FFXw, accessed August 19, 2024] Therefore, the burden of HZ and its complications could be substantial and shall rise as the ageing population increases.

Other treatment alternatives for HZ are antivirals and analgesics, but these are reportedly suboptimal due to limited efficacy against PHN, and minimal effect on quality of life. [J Eur Acad Dermatol Venereol 2017;31:20-29; Cochrane Database Syst Rev 2014:CD006866; J Pain 2005;6:356-363] Treatment delays are also possible due to the nonspecific symptoms at HZ onset or the low HZ burden awareness. [BMC Med 2010;8:37; J Dermatol 2016;43:1184-1187]

“Proactive prevention against HZ via vaccination would be an effective way to reduce the burden of HZ and its complications, and therefore deliver preventive care and support healthy ageing, which are key objectives of Healthier SG,” said the researchers.

Early HZ vaccination may alleviate the HZ burden, accrue its benefits over a longer period, and allow for allocation of resources for services targeting other diseases or conditions.

According to the investigators, the findings were robust under scenario and sensitivity analyses. “Mass vaccination with RZV is expected to greatly reduce the public health burden of HZ among SG individuals ≥50 years. The findings support value assessment and decision-making regarding public health vaccination strategies for HZ prevention in SG.”