Understanding Shingles and the Need for Vaccination
Shingles, also known as herpes zoster, is a painful rash with blisters caused by the reactivation of the varicella-zoster virus—the same virus that causes chickenpox [1.6.1]. After a person recovers from chickenpox, the virus remains dormant in the body and can reactivate years later, causing shingles [1.8.4]. The risk of reactivation increases with age, particularly after age 50, as the immune system naturally weakens [1.8.1]. The most common complication is postherpetic neuralgia (PHN), a long-term nerve pain that can be debilitating and last for months or even years [1.6.1]. With approximately one million cases occurring in the U.S. each year, vaccination is the most effective way to prevent the disease and its complications [1.8.2, 1.8.3]. For years, two vaccines were available: Zostavax and Shingrix.
What is Zostavax?
Zostavax, approved by the FDA in 2006, was the first vaccine used to prevent shingles [1.5.4]. It is a live, attenuated vaccine, meaning it contains a weakened form of the varicella-zoster virus [1.2.3]. The vaccine worked by introducing this weakened virus to the body, prompting an immune response to build protection against a future shingles outbreak [1.2.3]. It was administered as a single subcutaneous (under the skin) injection [1.2.3].
Zostavax Efficacy and Decline
The effectiveness of Zostavax was a significant improvement at the time of its release, but it had notable limitations. Its efficacy varied significantly with age. For individuals aged 60-69, it reduced the incidence of shingles by about 64%, but this dropped to 41% for those aged 70-79, and a mere 18% for people 80 and older [1.4.4]. Furthermore, its protection waned considerably over time, decreasing within three years and lasting only for about five years in total [1.2.4]. Because it was a live-virus vaccine, it was contraindicated for people with weakened immune systems [1.4.1]. Due to its lower efficacy and the availability of a superior alternative, Zostavax was discontinued in the United States as of November 2020 [1.5.3].
What is Shingrix?
Shingrix, approved by the FDA in 2017, represents a newer and more effective approach to shingles prevention [1.5.4]. Unlike Zostavax, Shingrix is a recombinant, non-live vaccine [1.2.2]. It is made from a specific protein of the zoster virus called glycoprotein E, combined with an adjuvant that boosts the body's immune response [1.2.3]. Because it contains no live virus, it is safe for individuals with compromised immune systems [1.2.3]. Shingrix is administered as a two-dose series of intramuscular injections, with the second shot given 2 to 6 months after the first [1.2.2].
Superior Efficacy and Durability
Shingrix has demonstrated significantly higher and more durable protection against shingles. In clinical trials, Shingrix was over 90% effective at preventing shingles in adults 50 and older [1.3.2]. Its efficacy remains high across age groups, showing 97% effectiveness in adults 50-69 and 91% in adults 70 and older [1.3.2]. Studies have also shown that this protection remains robust, staying high for at least seven years and showing nearly 80% efficacy up to 11 years after vaccination [1.9.2, 1.3.3]. The Centers for Disease Control and Prevention (CDC) now exclusively recommends Shingrix for the prevention of shingles in adults 50 and older, as well as for immunocompromised adults 19 and older [1.6.2, 1.6.3].
Head-to-Head Comparison: Zostavax vs. Shingrix
| Feature | Shingrix | Zostavax |
|---|---|---|
| Vaccine Type | Recombinant (non-live), adjuvanted [1.2.3] | Live, attenuated [1.2.3] |
| Availability in US | Currently recommended and available [1.5.4] | Discontinued as of Nov. 2020 [1.5.3] |
| CDC Recommendation | Preferred and recommended vaccine [1.6.2] | No longer recommended [1.2.2] |
| Number of Doses | Two doses, 2-6 months apart [1.2.2] | One dose [1.2.3] |
| Administration | Intramuscular (into the muscle) [1.2.3] | Subcutaneous (under the skin) [1.2.3] |
| Efficacy (Overall) | >90% in adults 50+ [1.3.2] | ~51% in adults 60+ [1.2.2] |
| Efficacy (Ages 70+) | ~91% [1.3.2] | 18% - 41% [1.4.4] |
| Durability | High efficacy for at least 7-11 years [1.3.1, 1.9.2] | Wanes significantly after 5 years [1.4.1] |
| Use in Immunocompromised | Yes, recommended for adults 19+ [1.6.2] | No, it was contraindicated [1.4.1] |
Side Effects
Both vaccines can cause side effects, though they differ in frequency and type. The most common side effects for both are injection-site reactions like pain, redness, and swelling [1.7.1]. However, Shingrix is associated with a higher rate of systemic side effects, which are generally mild to moderate and resolve within a few days. These can include muscle pain, fatigue, headache, shivering, and fever [1.7.2]. These reactions are a sign that the immune system is building a strong response. Zostavax side effects were generally less common and less severe [1.7.2]. In rare instances, Guillain-Barré syndrome (GBS) has been reported after Shingrix vaccination, but the FDA has determined that the vaccine's benefits outweigh this very low risk [1.2.2, 1.6.1].
Conclusion: The Clear Choice for Shingles Prevention
The primary difference between Zostavax and Shingrix lies in their technology, efficacy, and durability. Shingrix, a modern recombinant vaccine, offers over 90% protection that lasts for many years across all adult age groups [1.3.2, 1.3.1]. Zostavax, an older live-virus vaccine, provided much lower protection that decreased significantly with age and time [1.4.4, 1.4.1]. Due to its superior and longer-lasting effectiveness, the CDC strongly recommends that all eligible adults receive the two-dose Shingrix vaccine, even those who were previously vaccinated with Zostavax [1.6.2].
For more information, consult the CDC's recommendations on the shingles vaccine.
