Shingles (herpes zoster) is a painful condition caused by the reactivation of the varicella-zoster virus, the same virus responsible for chickenpox. After recovery, the virus remains dormant in nerve tissue and can reactivate years later, resulting in a blistering rash. The risk of developing shingles and its long-term complication, postherpetic neuralgia, increases significantly with age. Vaccination is the most effective preventative measure available.
Eligibility and Identifying the Vaccine
The currently recommended vaccine for shingles is the recombinant zoster vaccine (RZV), marketed under the name Shingrix. This vaccine is non-live, meaning it contains a protein component rather than a weakened form of the virus. This composition makes it the preferred vaccine, especially for individuals with weakened immune systems.
The standard recommendation is for all healthy adults aged 50 years and older to receive the two-dose series. Eligibility also extends to adults aged 19 and older who are immunodeficient or immunosuppressed due to disease or therapy. This includes people with conditions like HIV, cancer, or those who have had an organ transplant. Even if a person previously had shingles or received the older, live vaccine (Zostavax), they should still get the two-dose Shingrix series.
The Required Time Between Doses
The standard schedule for the Shingrix two-dose series specifies a window between the first and second dose. For most healthy adults, the second dose should be administered between two and six months after the first dose. This two-month minimum interval is necessary to allow the immune system to properly respond and “prime” itself.
Healthcare providers often aim for the second dose closer to the six-month mark to maximize the immune response. However, the two-month minimum may be utilized if a person needs to complete the series quickly, such as before starting immunosuppressive therapy. For those who are immunocompromised, the second dose can be given on a shorter schedule, specifically between one and two months after the first dose.
Guidance for Delayed Second Doses
If a person misses the end of the recommended six-month window for the second dose, it should be administered as soon as possible. Public health guidance confirms that the entire two-dose series does not need to be restarted, regardless of how long the delay has been.
The protection from the first dose is not lost, and a delayed second dose is still effective in completing the series. Real-world effectiveness studies show that the vaccine’s protective benefit is maintained even when the second dose is given after the recommended six-month period. The most important action is to get the second dose whenever it becomes available.
The Importance of Completing the Two-Dose Series
Completing the two-dose regimen is necessary to achieve the highest level of protection against shingles and its complications. The first dose initiates the immune response, and the second dose acts as a booster. This boosting effect leads to the long-lasting, robust protection of the complete series.
Real-world data shows a substantial difference in effectiveness between a partial and a complete series. While one dose may offer about 64% protection against shingles over four years, the full two-dose series maintains a high effectiveness rate, around 76% over the same period. Protection offered by a single dose tends to wane more substantially over time. The two-dose series is also highly effective at preventing postherpetic neuralgia.