In this article, our pharmacist discusses the main differences between Shingrix & Zostavax, two vaccines approved for shingles.
Overview
On October 25th, 2017 that CDC (Centers For Disease Control) announced that Shingrix is now the preferred vaccine for the prevention of shingles (also known as herpes zoster), replacing the long used Zostavax vaccine, which has been on the market since 2006. The announcement is based on the recommendation from the Advisory Committee on Immunization Practices (ACIP).
In addition to being the preferred vaccine for the prevention of shingles, the CDC also announced the following:
- Shingrix is recommended for healthy adults aged 50 years and older to prevent shingles and related complications.
- Shingrix is recommended for adults who previously received the Zostavax vaccine.
Not only is Shingrix the preferred vaccination, it is recommended for everyone 50 years old and over, even in those who ALREADY received Zostavax.
The new recommendations are estimated to increase the number of people needing vaccination by 62 million people!
These new recommendations beg the question, how is Shingrix different from Zostavax?
There are numerous differences between the two drugs. To summarize:
- Shingrix is more effective than Zostavax in preventing cases of herpes zoster (shingles).
- Shingrix contains an 'adjuvant', boosting vaccine effectiveness while Zostavax does not.
- Shingrix is NOT a live vaccine, unlike Zostavax, which is live.
- Shingrix does NOT need to be stored frozen. Zostavax needs to be stored in the freezer.
- Shingrix is given via an intramuscular injection while Zostavax is given via a subcutaneous injection.
- Shingrix is given as a 2 dose series, with doses spaced 2 to 6 months apart. Zostavax is given as a single dose.
- Shingrix is recommended for all individuals aged 50 years old and over. Zostavax is recommended for healthy individuals aged 60 years old and over.
Below, we discuss these differences in detail.
Vaccine Effectiveness
According to published data, Shingrix reduced the risk of developing shingles by 97.2% when compared to placebo. In the large clinical trial (ZOSTER-006 Trial):
- 7,344 people over the age of 50 were given the Shingrix vaccine. There were 6 reported cases of shingles over a period slightly longer than 3 years.
- 7,415 people over the age of 50 were given a placebo (i.e. no vaccine). There were 210 reported cases of shingles over a period slightly longer than 3 years.
- Unlike Zostavax, which has a marked decrease in efficacy in older populations, Shingrix has similar effectiveness in all age groups.
Adapted From Shingrix Package Insert
You may notice that the above table for Shingrix shows 'Incidence Rate of HZ Per 1000 person-years". This is a way to normalize data based on the length of the clinical trial.
For instance, the Shingrix trial had an average follow up time of 3.1 years. In the overall population that received the vaccine, that amounts to 23,297 years (7,344 patients times 3.1 years). The number of cases of shingles during this time period was 6. Therefore, the incidence per 1000 years is 0.3 (6 cases of shingles divided by 23,297 years multiplied by 1,000).
Zostavax has an overall efficacy of 51%, less than Shingrix and as mentioned above, it significantly loses effectiveness in older populations.
Other Differences
Adjuvant
In addition to the actual herpes zoster vaccine, Shingrix contains an immune response boosting 'adjuvant' known as AS01B. Adjuvants are a common component of many vaccines and are classified as a 'molecule that can boost the potency, quality or longevity of a specific immune response'. Zostavax does not contain an immune boosting adjuvant.
Live Vs. Non-Live
Shingrix is a recombinant, non-live vaccine unlike Zostavax, which is a live vaccine. Non-live vaccines typically have less stringent storage requirements and that is the case with Shingrix. Shingrix must be refrigerated while Zostavax must be frozen.
In addition, most live vaccines like Zostavax need to be used with caution in patients that may be immunocompromised as this can increase the risk of adverse reactions. Although Shingrix is more likely to be safer in this patient population, there is no definitive information regarding this.
Administration
Shingrix is given via intramuscular injection in a two dose series, with each dose separated by 2 to 6 months. Zostavax is given via subcutaneous injection as a single dose.
Indication
Shingrix has is approved and recommended for use in people aged 50 years old and over. Zostavax is also approved for use in people aged 50 years old and over. However, immunization guidelines only recommend use in people aged 60 years old and over (due to concerns of lasting effectiveness at older ages).
Other Information
The CDC recommends that Shingrix be given to people over 50, regardless of their immunization history with Zostavax. It can be given as soon as 8 weeks after Zostavax had been administered.
