postherpetic neuralgia increase with advancing age, occurring in 20% of people age 60–65 years old who have had herpes zoster, and in more than 30% of people over 80 years old. Prevention Primary prevention Shingles vaccination is the only way for adults to be protected against both shingles and postherpetic neuralgia, with two vaccines approved for use in people over age 50. The zoster vaccine Shingrix provides around 90% protection from postherpetic neuralgia, and has been used in many countries since 2017. The earlier vaccine Zostavax provides lesser protection against shingles, and PHN. The varicella vaccine is approved for infants to prevent chickenpox, which also protects against PHN from a herpes zoster infection. Vaccination decreases the overall incidence of virus reactivation, and also decreases the severity of disease development and incidence of PHN if reactivation does occur. Secondary prevention A 2013 Cochrane meta-analysis of 6 randomized controlled trials (RCTs) investigating oral antiviral medications given within 72 hours after the onset of herpes zoster rash in immunocompetent people for preventing postherpetic neuralgia (PHN) found no significant difference between placebo and aciclovir. Additionally, there was no significant difference in preventing the incidence of PHN found in the one RCT included in the meta-analysis that compared placebo to oral famciclovir treatment within 72 hours of HZ rash onset. Studies using valaciclovir treatment were not included in the meta-analysis. PHN was defined as pain at the site of the dermatomic rash at 120 days after the onset of rash, and incidence was evaluated at 1, 4, and 6 months after rash onset. Patients who are prescribed oral antiviral agents after the onset of rash should be informed that their chances of developing PHN are no different than those not taking oral antiviral agents. Treatment The pain from postherpetic neuralgia can be very severe and requires immediate treatment. There is no treatment which modifies the course of the disease and management primarily aims to control symptoms. Medications Topical medications Medications applied to the skin can be used alone if the pain from PHN is mild or in combination with oral medications if the pain is moderate to severe. Topical medications for PHN include low-dose (0.075%) and high-dose (8%) capsaicin and anesthetics such as lidocaine patches. Lidocaine patches (5% concentration) are approved in the United States and Europe to treat PHN though evidence supporting their use is limited. A meta-analysis of multiple small placebo-controlled randomized controlled