Shingles, or herpes zoster, causes a painful rash and potential long-term nerve pain, posing a significant health concern for older adults, which vaccination is designed to prevent. The core question regarding the shingles vaccine concerns its composition: whether it contains a live virus. Historically, the answer was yes, as the first widely available vaccine, Zostavax, utilized a live, weakened virus to prompt an immune response. The current standard of care, however, is a newer product called Shingrix, and it is definitively a non-live vaccine. This shift from a live virus formulation to a non-live component marks a major advancement in how protection against the varicella-zoster virus is achieved.
The Live and Non-Live Shingles Vaccines
The initial shingles vaccine, Zostavax, was classified as a live attenuated virus vaccine, meaning it contained a living but weakened form of the varicella-zoster virus (VZV). This weakened virus, the Oka/Merck strain, was present in a high concentration. The mechanism of action relied on the live virus replicating minimally within the recipient to mimic a natural, mild infection, thereby stimulating a robust immune memory against VZV. The vaccine was administered as a single dose via a subcutaneous, or under-the-skin, injection.
The newer vaccine, Shingrix, employs an entirely different formulation and is known as a recombinant subunit vaccine. This non-live vaccine does not contain any whole, live, or dead viruses but instead uses only a single, purified component of the virus. It contains the VZV surface protein called glycoprotein E (gE), which is involved in viral entry and is highly immunogenic. The gE protein component is produced using recombinant DNA technology and is combined with a powerful substance called an adjuvant.
The inclusion of the AS01B adjuvant system is a defining feature of the Shingrix vaccine, which aims to maximize the body’s immune reaction to the gE protein. This adjuvant contains two immune-enhancing molecules that work together to boost the innate immune system’s response. This combination helps ensure a strong and long-lasting defense by generating a high level of anti-gE antibodies and T-cells, despite the absence of a live virus. Shingrix is administered as an intramuscular injection, typically into the deltoid muscle of the upper arm.
Safety and Efficacy Differences
The fundamental difference in vaccine composition has significant implications for both safety and effectiveness. Because Zostavax contained a live, replicating virus, it carried a theoretical risk of causing a full-blown infection in individuals whose immune systems were compromised. For this reason, the live attenuated vaccine was contraindicated for people with conditions like severe immunodeficiency, certain cancers, or those on immunosuppressive therapy. The non-live nature of Shingrix largely eliminates this concern, making it safe for use in immunocompromised adults, as it contains only a viral protein fragment.
In terms of efficacy, the non-live Shingrix vaccine demonstrated significantly higher and more durable protection compared to its live predecessor. Across clinical trials, Shingrix was found to be approximately 97% effective in preventing shingles in adults aged 50 to 69, a protective level that remained high at 91% for those aged 70 and older. In comparison, Zostavax offered an overall effectiveness of about 51% in preventing shingles, and this protection declined substantially over time, dropping to as low as 18% in those aged 80 and older after several years.
The duration of protection also differs markedly between the two vaccine types. Studies have shown that the high efficacy provided by Shingrix is sustained for at least seven years, with some data suggesting protection can last a decade or more. Conversely, the protection from the live Zostavax vaccine waned steeply, often becoming less than 35% effective six years after vaccination. The presence of the AS01B adjuvant causes more common, temporary post-vaccination reactions, including injection site pain, redness, swelling, muscle aches, and fatigue, which are generally mild to moderate in severity.
Current Vaccination Recommendations
The superior performance and broader safety profile of the non-live vaccine have led to clear guidance from health authorities regarding its use. Shingrix is now the only shingles vaccine available in the United States and is the preferred vaccine globally. The Centers for Disease Control and Prevention (CDC) recommends the recombinant vaccine for all healthy adults beginning at age 50. It is also recommended for immunocompromised adults aged 19 and older, given the safety advantages of its non-live formulation.
Shingrix requires a two-dose schedule to achieve maximum protection against shingles and its complications. For adults with healthy immune systems, the second dose is administered between two and six months after the first. Immunocompromised individuals may receive the second dose on a shorter schedule, generally one to two months after the initial dose, to complete the series sooner.
Anyone who previously received the live Zostavax vaccine should still be revaccinated with the two-dose Shingrix series. This is advised due to the substantial difference in both the level of protection and the duration of efficacy offered by the newer vaccine. While Zostavax was discontinued in the U.S. in November 2020, the current guidance ensures that those who received the older product can benefit from the enhanced protection of the non-live formulation.