Shingrix is not an mRNA vaccine. It is designed to protect adults from herpes zoster, commonly known as shingles, which is caused by the reactivation of the varicella zoster virus. Shingrix uses a different and more established technology platform than the messenger RNA (mRNA) vaccines. Shingrix is classified as a recombinant subunit vaccine, a category that relies on delivering a purified fragment of the virus rather than genetic code.
Shingrix’s Vaccine Classification
Shingrix is formally categorized as an adjuvanted recombinant subunit vaccine, meaning it contains only specific, purified components of the virus rather than the entire weakened or inactivated pathogen. The main active ingredient is glycoprotein E (gE), a protein naturally found on the surface of the varicella zoster virus. This particular protein was selected because it is highly effective at triggering a protective immune response against the virus.
The vaccine is recommended for individuals aged 50 years and older, and certain immunocompromised adults aged 18 and up. It is administered as a two-dose series, typically given between two and six months apart. The non-live nature of this vaccine makes it suitable for people with weakened immune systems.
An adjuvant system, known as AS01B, is also included to significantly boost the body’s reaction to the purified protein. Without this immune-enhancing component, the isolated glycoprotein E alone would not reliably generate the strong, long-lasting immunity needed for effective protection. This combination of a manufactured protein and a powerful adjuvant defines the vaccine’s specific classification.
How Recombinant Subunit Technology Works
Recombinant subunit technology focuses on isolating and mass-producing a single, recognizable protein from the target pathogen. For Shingrix, the genetic blueprint for glycoprotein E is inserted into the DNA of host cells, such as Chinese hamster ovary (CHO) cells, which then act as factories. These modified cells are grown in large bioreactors, where they produce quantities of the gE protein.
Once manufactured, the glycoprotein E is harvested and purified, removing all traces of the host cells and viral genetic material. The final product is the finished protein, a specific “subunit” of the virus, which the immune system can learn to recognize. This method ensures that the vaccine cannot cause the disease because it contains no living or complete viral particles.
The immune response is significantly amplified by the proprietary AS01B adjuvant system, which is a key scientific element of Shingrix’s high efficacy. This adjuvant is composed of two natural immune-stimulating compounds: Monophosphoryl Lipid A (MPL) and QS-21. These components are packaged into a liposomal formulation.
The components of the AS01B work synergistically to alert the innate immune system to the presence of the gE protein. MPL triggers a specific pathway by binding to a receptor on immune cells called Toll-like Receptor 4, while QS-21 is thought to activate a different cellular complex, the NLRP3 inflammasome. This dual action strongly activates antigen-presenting cells, which then efficiently display the gE protein to specialized T-cells and B-cells. This process results in the robust and sustained cellular and humoral immunity that is necessary to prevent shingles in older adults whose immune responses are naturally declining.
Comparing Shingrix to mRNA Vaccines
The fundamental difference between Shingrix and mRNA vaccines lies in what is injected and how the immune response is generated. Shingrix injects the finished glycoprotein E protein, manufactured externally in a laboratory. The body’s immune cells directly encounter this protein and the adjuvant at the injection site, triggering the protective response.
In contrast, an mRNA vaccine delivers a strand of messenger RNA, which is a set of genetic instructions, encased in a protective lipid nanoparticle. Upon injection, the recipient’s own muscle cells absorb the mRNA, read the instructions, and temporarily manufacture the target viral protein internally. The body is effectively turned into a temporary vaccine factory, producing the antigen itself, which the immune system then detects and learns to fight.
This distinction leads to practical differences in handling and distribution. The purified protein in the Shingrix vaccine is stable, requiring only standard refrigeration storage. This stability makes it easier to transport and store in most healthcare settings.
The mRNA technology allows for faster development and manufacturing timelines because the process involves synthesizing genetic code rather than growing and purifying proteins. While there is currently no approved mRNA vaccine for shingles, several pharmaceutical companies are developing candidates that they believe could be produced more efficiently and potentially offer a more tolerable shot. Both the recombinant subunit and the mRNA approach are techniques that successfully guide the immune system to recognize a specific viral protein, but they achieve this goal through separate biological pathways.