How do Self-Amplifying RNA Vaccines Work?

In late November 2023, regulatory authorities in Japan approved a new SARS-CoV-2 vaccine. Unlike earlier messenger RNA (mRNA) vaccines used to protect against COVID-19, this one relies on a technology called self-amplifying mRNA, or saRNA. Though researchers have long pursued saRNA-based vaccines, this represents the first full approval for the technology in humans and marks an exciting advance in the ongoing development of mRNA vaccines.

Continue reading for an overview of how saRNA vaccines work and some of their advantages relative to standard mRNA vaccines.

A syringe withdraws clear liquid from a sealed glass vial.
 A new type of COVID-19 mRNA vaccine, a self-amplifying RNA vaccine, was recently approved in Japan.
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COVID-19 and Type 1 Diabetes: Exploring the Potential Link

Prior to the COVID-19 pandemic, the incidence of adolescent type 1 diabetes was steadily increasing at a rate of 1.9% per year in the United States and 3-4% per year in European countries (3,7). Since the pandemic, however, several studies have reported an unprecedented surge in type 1 diabetes in children and teenagers.

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Reviewing the Importance of circRNA

In recent years following the COVID-19 pandemic, RNA has gained attention for its successes and potential use in vaccines and therapeutics. One avenue of interest in RNA research is a non-coding class of RNA first identified almost 50 years ago, circular RNA (circRNA).

In 1976, Sanger et al. first identified circRNA in plant viroids, and later additions to the field found them in mice, humans, nematodes, and other groups. Unlike linear RNA, circRNA are covalently closed loops that don’t have a 5′ cap or 3′ polyadenylated tail. Following its discovery, researchers thought circRNA was the product of a rare splicing event caused by an error in mRNA formation leading to low interest in researching the subject (1).

In the early 2010s, following the development of high throughput RNA sequencing technology, Salzman et al. determined that circRNAs were not a result of misplicing, but a stable, conserved, and widely sourced form of RNA with biological importance. Since noncoding RNA makes up the majority of the transcriptome it’s an incredibly important field of study. We now recognize circRNAs for their potential as disease biomarkers and importance in researching human disease (2).

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Custom in vitro Transcription Reagents for Manufacturing RNA Therapeutics

Doctor filling syringe

Research into vaccines based on RNA began decades ago when scientists theorized that they could harness RNA to produce viral proteins within a cell, prompting a protective immune response. RNA vaccine research drew scientists’ attention during the development of SARS-CoV-2 vaccines during the COVID-19 pandemic, which opened the door for research targeting other diseases with RNA-based therapeutics.

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Confronting an Emerging Pathogen: Candida auris

Candida auris illustration
Candida auris is a fungal infection sweeping through healthcare sites across the U.S.

HBO’s The Last of Us has successfully brought fungal pathogens to the forefront of the pandemic discourse, raising questions as to whether a fungus could really pose a significant threat to humans. While scientists agree that the fungus featured in the show, cordyceps, won’t be making the required inter-species jump any time soon, there is a fungal pathogen that has been taking root in hospitals across the U.S. which gives some cause for concern: Candida auris.

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mRNA Vaccine Manufacturing: Responding Effectively to a Global Pandemic

We’ve learned a few important lessons from the COVID-19 pandemic.

Perhaps the most significant one is the importance of an early and rapid global response to the initial outbreak. A coordinated response—including widespread use of masks and other personal protective equipment (PPE), travel restrictions, lockdowns and social distancing—could save lives and reduce long-term health effects (1). Widespread availability of effective vaccines goes hand in hand with these measures.

New Boosters to Fight Omicron

Last month, Pfizer/BioNTech announced the US Food and Drug Administration (FDA) had granted emergency use authorization (EUA) for a new adapted-bivalent COVID-19 booster vaccine for individuals 12 years and older. This vaccine combines mRNA encoding the wild-type Spike protein from the original vaccine with another mRNA encoding the Spike protein of the Omicron BA.4/BA.5 subvariants. Moderna also announced FDA EUA for its new Omicron-targeting COVID-19 booster vaccine. The Omicron variant of SARS-CoV-2 shows multiple mutations across its subvariants, and it is currently the dominant SARS-CoV-2 variant of concern across the world.

Genomic epidemiology of SARS-CoV-2 with subsampling focused globally over the past 6 months. This phylogenetic tree shows evolutionary relationships of SARS-CoV-2 viruses from the ongoing COVID-19 pandemic. Image from; generated September 20, 2022

Booster doses of vaccines have become a way of life, both due to declining effectiveness of the original vaccines especially in older adults (2), and the rapid mutation rate of SARS-CoV-2 (3). Clinical data for the new Pfizer/BioNTech booster vaccine showed superior effectiveness in eliciting an immune response against Omicron BA.1 compared to the original vaccine. Previously, Moderna published interim results from an ongoing phase 2-3 clinical trial, showing that the new bivalent booster vaccine elicited a superior neutralizing antibody response against Omicron, compared to its original COVID-19 vaccine (4).

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COVID-19 Intranasal Vaccines: Right on the Nose?

Last updated April 28, 2023

covid-19 intranasal vaccines

COVID-19 is still a global pandemic. Around the world, as of 5:40pm CEST, 26 April 2023, there have been 764,474,387 cumulative confirmed cases of COVID-19, including 6,915,655 deaths, reported to the World Health Organization. As of 24 April 2023, a total of 13,325,228,015 vaccine doses have been administered. The adoption of vaccines worldwide continues to increase, yet periodic spikes and surges in infection rates continue to occur with new SARS-CoV-2 variants, such as that observed in Australia in Jan 2022. Vaccine booster doses provide effective protection against developing severe disease and hospitalization, but vaccine adoption and distribution face ongoing challenges in low- and middle-income (LMIC) countries (1). The development of intranasal vaccines could help alleviate some of the challenges in these areas. Therapeutic interventions for those already infected are in development, with one (Paxlovid) currently available under emergency use authorization (EUA) in the US.

Cumulative COVID-19 statistics by country: WHO COVID-19 Dashboard. Geneva: World Health Organization, 2020. Available online: (last cited: April 28, 2023).

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Detecting SARS-CoV-2 In Wastewater: The New Frontier in Pandemic Surveillance

Tracking the spread of COVID-19 has been a tremendous challenge throughout the pandemic, but doing so is a key step toward containing the virus. Many communities have relied on patient testing and contact tracing, with limited success. In search of better methods, some countries have made inroads in a different form of disease surveillance: wastewater-based epidemiology (WBE). This approach involves testing wastewater for the presence of pathogens, primarily through DNA and RNA analysis, and has proved to be an accurate and highly effective way to keep tabs on the prevalence and progression of COVID-19 at the population level.

Switzerland is among those countries that have implemented WBE in their efforts to stay ahead of the pandemic. Since WBE first emerged in 2020 as a promising tool, several Swiss laboratories undertook wastewater testing, and protocols were established early.

“At the beginning, the methods to actually detect coronavirus in wastewater were rather laborious and complicated, and involved a lot of resources,” said Dr. Claudia Bagutti, microbiologist and molecular biologist in the State Laboratory of Basel-City, Switzerland.

Bagutti heads a small team performing applied biosafety research. In 2020, her lab was tasked with developing an assay for detecting COVID-19 in wastewater. However, the available methods were prohibitively complex and resource intensive.

In the meantime, researchers at Promega recognized that Promega products and methodologies could potentially be applied to WBE and set to work developing simpler and more efficient method for wastewater analysis. In the spring of 2021, Bagutti’s team decided to try adopting this method.

“Promega had a very nice method which was less laborious and much easier to handle, and that’s why we gave it a try,” said Bagutti.

In the ensuing study, Bagutti and her team analyzed effluent from the catchment area of one municipal wastewater plant in Switzerland. They examined the total wastewater output of around 270,000 people. Viral RNA was extracted using Promega’s Maxwell® RSC Environ Wastewater TNA Kit. The number of RNA copies present, representing the overall concentration of COVID-19 in each sample, was determined via quantitative reverse transcriptase (RT-qPCR) using the GoTaq® Enviro Wastewater SARS-CoV-2 Systems, also from Promega. The viral RNA was subsequently sequenced with next generation sequencing, and the results correlated quite well with the COVID-19 cases in the catchment area. Remarkably, this study detected the Omicron variant in a wastewater sample one day prior to the first reported case identified through patient testing.

“We observed a similar spread to most other western countries with respect to the time of the first discovery of these variants,” said Bagutti. “We were also able to demonstrate the presence [of Omicron] in the wastewater before it came up in a sample of a COVID-19 patient test, which of course shows the usefulness of wastewater monitoring for the prediction of new variants and infection dynamics.”

WBE is especially promising in that it provides population-level data independent of patient testing. Health departments can be alerted to the presence of COVID-19 earlier than would otherwise be possible with traditional testing and can take precautions to contain the spread. In creating a more user-friendly method for wastewater analysis, Promega has opened the door for more laboratories to conduct WBE, which could provide communities around the world with the information they need to preempt the progression of COVID-19.

“The Promega method is very straightforward to handle,” said Bagutti. “It only takes a small volume of wastewater, which makes it handy. It’s less time-consuming compared to the methods which were in the literature at the beginning of the pandemic, and it just works very well. We also did experience great support from Promega.”

At this point, much of the wastewater analysis performed in Switzerland is done with the Promega method, including in federal, state or private labs. The swift advance of WBE in Switzerland speaks to the colossal effort put forth both by Promega researchers in developing the necessary products and methodologies, as well by those labs that have made use of Promega’s products to monitor COVID-19 in wastewater.

“It’s really been a success story for us, from the beginning,” said Bagutti.

Learn more about Promega’s work with wastewater-based epidemiology.

Cytochrome P450 Inhibition: Old Drug, New Tricks

multiwell screening plate and various pills on a table

Cytochrome P450 (CYP) inhibitors are often used as boosting agents in combination with other drugs. This drug development strategy is front and center for Paxlovid, the new anti-SARS-CoV-2 treatment from Pfizer. Paxlovid is a combination therapy, comprised of two protease inhibitors, nirmatrelvir and ritonavir. It significantly reduces the risk of COVID-19 hospitalization in high-risk adults and is ingested orally rather than injected, which is an advantage over other SARS-CoV-2 treatments, such as Remdesivir.

Nirmatrelvir was originally developed by Pfizer almost 20 years ago to treat HIV and works by blocking enzymes that help viruses replicate. Pfizer created another version of this drug to combat SARS in 2003, but, once that outbreak ended, further development was put on pause until the advent of the COVID-19 pandemic. After developing an intravenous form of nirmatrelvir early in the pandemic, Pfizer created another version that can be taken orally and combined it with ritonavir.

When ritonavir was originally developed, it wasn’t considered particularly useful because it metabolized so quickly in the body. Now it is recognized as a pharmacokinetic enhancer in combination with other drugs. Ritonivir inhibits CYP3A4, an enzyme which plays a key role in the metabolism of drugs and xenobiotics. By inhibiting CYP3A4, ritonivir slows the metabolism of other drugs. In the case of Paxlovid, this allows nirmatrelvir to stay in the body longer at a high enough concentration to be effective against the virus. This ultimately means that patients can be given lower doses of the drug with reducing efficacy.

Diagram of Nirmaltrelvir mechanism of action.
Nirmatrelvir inhibits the viral 3CL protease, so that functional, smaller viral proteins cannot be produced.
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Antibody Correlates of Protection for mRNA Vaccine

Identifying correlates of protection, or biological markers that correlate with a certain level of protection from disease helps public health experts assess vaccination performance. Picture of a COVID-19 vaccine vial.

In the rapidly shifting context of a pandemic, public health officials need a way to quickly assess how vaccinations perform in changing situations. One approach is to identify correlates of protection, or biological markers that correlate with a certain level of protection from disease. This tool is used to assess the design and formulation of annual influenza vaccines, as immune system markers that correlate with protection from flu can give developers a sense of how effective the vaccine might be for different population groups. Though they are not a replacement for rigorous clinical trials, correlates of protection can provide meaningful and predictive data for vaccine developers with smaller trial sizes and less time.

A study published in November 2021 indicated that levels of binding antibodies and neutralizing antibodies for the SARS-CoV-2 virus in blood serum are correlates of protection for Moderna, Inc.’s COVE phase 3 clinical trial of their mRNA COVID-19 vaccine.

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