mRNA Vaccine Technology

In 2020, a year that will live in infamy, the collective humanity of the world was suddenly attacked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or COVID-19, which caused an incalculable level of damage to human health, psyche, and global economies (Cutler DM et al., 2020). Phylogenetic analysis points to a zoonotic origin where the novel coronavirus is closely related to coronaviruses circulating in a species of horseshoe bat (Rhinolophus affinis), exhibiting a 98.7% nucleotide identity to a partial sequence of an RNA-dependent RNA polymerase gene from bat coronavirus strain BtCoV/4991 (Chen L et al., 2020) and sharing an overall 96.2% sequence identity with the genome of bat coronavirus RaTG13 (Zhou P et al., 2020). These bat coronaviruses were discovered in the Chinese province of Yunan in 2013 (Ge XY et al., 2016).

A key component of the natural origin hypothesis is that the virus somehow accrued a pangolin receptor binding domain (Zhang T et al., 2020) in the jump to humans and then had an early epicenter that has been traced to the Huanan Seafood Wholesale Market in Wuhan, China (Worobey M et al., 2022); however, reports, which cannot be precluded, continue to persist indicating that the virus is nonzoonotic and moreover is a product of genetic engineering (Segreto R et al., 2020; Borsetti A et al., 2022; Gøtzsche PC et al., 2022; Hassan SS et al., 2022).

At this current juncture, in 2023, as the COVID-19 tsunami and the angst surrounding it have largely dissipated, it is an appropriate time to reflect and examine the key mRNA vaccine milestones that facilitated the development of the two mRNA vaccines, COMIRNATY^® (BNT162b2), which is made by Pfizer and BioNTech, and Spikevax^® (mRNA-1273), which is made by Moderna, that collectively have served in the United States as the main weapons in the arsenal against the COVID-19 pandemic.

Genesis of the mRNA vaccine technology

Unlike the Bible, which describes a clear delineation between chaos and order and the events culminating in a defined world, the evolution of the mRNA vaccine field is far from linear. Trying to mark the true beginning of the field is somewhat of a subjective judgment that can only be rendered after what is akin to first trying to fix a tangled ball of yarn. That being said, by anyone reasonable person’s precepts, research into mRNA vaccines has been going on for decades and was well underway last century.

The earliest glimpses of the technology underlying mRNA vaccines can first be found way back in the early to mid-1970s where, although primitive by today’s state-of-the-art, it was recognized that the transfer of RNA extracts from sensitized lymphoid tissues could be used to transfer tumor-specific delayed hypersensitivity in vitro to normal guinea pig peritoneal exudate cells (Paque RE et al., 1973), and local tumor regression could be achieved using syngeneic or xenogeneic "tumor-immune" RNA extracts (Schlager SI et al., 1975). The next big leap occurred some three years later when a target cell delivery of immune RNA by liposomes produced a dose-dependent stimulation up to 12 times that achieved by in vitro methods with naked immune RNA (Magee WE et al., 1978), and it was recognized that target-directed liposomes provide a highly efficient delivery system for immune RNA in a form that is protected from RNase action and is markedly effective in the stimulation of lymphocytes.

A seminal event in the development of mRNA delivery was the extension of a broadly applicable in vitro DNA transfection technique (Felgner PL et al., 1987) to deliver a synthetic Photinus pyraisluciferase mRNA into NIH/3T3 mouse cells. This study was noteworthy for the following reasons: the mRNA for a complete gene was made by in vitro means; the mRNA underwent modification to optimize translation (capped and untranslated beta-globin sequences were added, which produced at least 1000-fold more luciferase protein than mRNAs lacking these elements), and the mRNA was encapsulated in cationic lipids, the composition of which was adjustable. (Malone RW et al., 1989).

There has been much debate online, in the press, and on television concerning the proper credit that should be duly assigned to the report’s primary author, Dr. Robert Malone, for the development of today’s mRNA vaccines. Certainly, this study forms the bedrock technology upon which the mRNA vaccines are predicated; however, part of the historical assessment is dependent upon whether the mRNA vaccines are true vaccines or fall more into the realm of gene therapies; hence, deciding upon if Dr. Malone is the father, godfather, stepfather, grandfather, great grandfather, or third cousin twice removed is deferred to posterity.

Further technological advances post Dr. Malone’s work and up to the first mRNA vaccines are described in detail in the mRNA vaccine history review by Dolgin E, 2021. Hurdles that were overcome include lessening inflammatory and reactogenic responses (Karikó K et al., 2005) and improving vaccine safety and enhancing mRNA translation efficacy. Advances in optimizing in vitro-transcribed mRNA brought mRNA-mediated therapy closer to the clinic (reviewed in Jeeva S et al., 2021).

Influenza was the first infectious agent against which mRNA vaccines were tested in animal models. The induction of anti-influenza cytotoxic T lymphocytes (CTL) in vivo by immunizing mice with liposomes containing mRNA encoding the influenza virus nucleoprotein (NP) was reported (Martinon F et al., 1993). Later, it was shown that mRNA vaccines induce balanced, long-lived and protective immunity to influenza A virus infections in even very young and very old mice and that the vaccine remains protective upon thermal stress. (Petsch B et al., 2012). Finally, modified non-replicating mRNA encoding influenza H10 encapsulated in lipid nanoparticles (LNP) induced robust B-cell responses in non-human primates (Lindgren G et al., 2017).

At the dawning of the age of COVID, mRNA vaccines had debuted in the clinic but without much ballyhoo. Although manufacturing, scalability, and delivery challenges had been addressed, safety and efficacy issues were not entirely elucidated. For example, investigators enrolled 101 healthy, rabies-unvaccinated volunteers in a phase 1 study for a prophylactic rabies vaccine, and injection site reactions occurred in >90%, systemic reactions in 78%, and one possibly vaccine-related serious event (moderate Bell palsy) was transient. (Alberer M et al., 2017) This study was sponsored by Curevac and used unmodified DNA. Around the same time (Aug 19, 2019), the Moderna mRNA-1893 Zika vaccine received FDA fast track designation. Moderna’s platform relied on chemically modified bases, but at the time, had advanced nine mRNA vaccine candidates for infectious diseases into people for testing, with only one progressing to a larger-phase trial (Dolgin E, 2021).

Operation Warp Speed

In a best-case scenario, all of the bugs had been worked out of mRNA vaccine technology and it was now ready for opening night and wide-scale use. The COVID-19 pandemic, or more appropriately Operation Warp Speed (OWS), was the deciding factor that raised the curtains on the mRNA vaccine act. As per the Department of Health and Human Services’ official description, “OWS is a partnership among components of the Department of Health and Human Services (HHS), including the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the National Institutes of Health (NIH), and the Biomedical Advanced Research and Development Authority (BARDA), and the Department of Defense (DoD)” that was initiated with the intent of delivering 300 million doses of an effective COVID 19 vaccine by January 2021. Some $18 billion were spent toward this endeavor (Lancet Commission, 2021). Indeed, in that calendar year, mRNA vaccine administration was conducted on a scale that was orders of magnitude greater than ever previously used in the clinic. Creating vaccines and having results from clinical studies hardly a year after a the identification of a never-before-seen virus was remarkable, to say the least.

To put this in proper perspective, consider that ten-plus years is a reasonable timeline in which to complete the development of a vaccine, and most vaccines do not even make it to the market; some make it but do not reach original product goals, and a few make it and perform as designed (Sanofi-Pasteur (Swiftwater, PA), 2017). Hence, the large-scale readiness of the COVID-19 mRNA vaccine platform was a vaccinology hole-in-one if there ever were one, and it all seemed too good to be true. Such skepticism, however, was countered by Dr. Anthony Fauci, the former top U.S. infectious disease expert who told the Associated Press in December 2020, “The speed is a reflection of years of work that went before. …That’s what the public has to understand.” (PBS News Hour)

Initial enthusiasm notwithstanding, in the few short years since the COVID-19 mRNA vaccines have been available, even a casual perusal of the Vaccine Adverse Events Reporting System (VAERS), reveals more serious adverse events from these two vaccines than all the other available vaccines combined over the past 30 years. Additionally, it is highly likely that anyone reading this article has personally either experienced a breakthrough infection or knows others who have had one or even several post-vaccination infections.

The OWS funds enabled the large-scale manufacture, distribution, affordability, and administration of the COVID-19 mRNA vaccines but could not buy the requisite time needed for the proper oversight and expansion of this technology. Even Bill Gates, who frequently and freely opined on the pandemic and the benefits of the mRNA technology, recently stated that “We also need to fix the three problems of [COVID-19] vaccines. The current vaccines are not infection-blocking. They’re not broad, so when new variants come up, you lose protection, and they have very short duration, particularly in the people who matter, which are old people.” But rest assured, “every one of those things is fixable.” (Speaking at Australia’s Lowy Institute, 2023)

Alternative technologies

Infinitely more important than resolving Dr. Malone’s true contribution to the field is deciphering mRNA vaccine safety, efficacy, and potential means for improvement. What is possible is that the mRNA technology, however exciting and promising, may have been prematurely advanced at the expense of other technologies that were more vetted, as or even more safe and efficacious, or just less flashy. Most notably, the tried-and-true gold standard comprising a live attenuated virus vaccine was written about but was never developed (Okamura S et al., 2021).

Real-world comparisons are not facile as countries often used a battery of different vaccines that were based on different modalities to address the pandemic. What is presented in Table 1 is a rudimentary comparison of a set of countries that achieved high vaccination rates. It is unclear if the mRNA vaccines offered an advantage over other platforms; in fact, a densely populated country like India appeared to fare relatively well, even without relying on the mRNA technology as a mainstay.

Table 1. A Global Perspective of COVID-19 Platforms Used Across Countries with High Rates of Vaccination

¹Source Worldometer (accessed 05 February 2023). ²United States 399 million Pfizer, 250 million Moderna, 14-15 million Janssen (based on replication deficient adenovirus 26 virus expressing full-length S protein). ³Deal between Pfizer and the Netanyahu-led government in which Israel locked in an early supply of Pfizer-BioNTech vaccines in exchange for providing data to Pfizer. As a result, virtually no other vaccines were available to the general public. ⁴As per government website accessed on 05 February, 2023: 24,922,054 total doses have been administered. It is not clear what the relative distribution between the 2 platforms is. ⁵Based on the incidence rate ratios, the vaccine effectiveness in fully vaccinated individuals was 80%, 92%, and 97% in preventing COVID-19-related hospital admissions, critical care admissions, and death, respectively, when compared to the non-vaccinated group (Al Kaabi N at al, 2022; Ismail AlHosani F et al, 2022). ⁶As per Wikipedia (accessed 05 February, 2023): 950,937,435 people corresponding to 87.7% of the population were fully vaccinated. ⁷Estimated vaccine efficacy (VE) against severe illness was 93·3% (95% CI: 92·1-94·3) in partially- vaccinated and 98·2% (95% CI: 97·9-98·5) in fully-vaccinated and against death was 94·1% (95% CI: 92·5-95·4) in partially-vaccinated and 98·7% (95% CI: 98·3-99·0) in fully-vaccinated. VE exceeded 92·0% in all age groups (Más-Bermejo PI .et al, 2022).. ⁸11,976,900 total doses administered (New Zealand Ministry of Health website. Accessed 05 February, 2023).⁹265,906,862 total doses administered (Wikipedia, accessed 05 February 2023).

Final thoughts

As best said in a line from the song ‘Games People Play’ by the Alan Parsons Project band, “Where do we go from here?”

The following are several unmet needs for the COVID-19 mRNA vaccines, and all future mRNA vaccines for that matter, that need to be addressed and/or evaluated:

• A thorough, real-world data analysis of the different COVID-19 platforms across the different platforms across different countries is very much in order.
• Clinical studies that are designed to detect a reduction in any serious outcomes, such as hospital admissions, use of intensive care, transmissibility, or deaths. The COVD-19 mRNA vaccine trials were deficient in this regard (Doshi P et al., 2020).
• As reviewed by Doulberis M et al., 2021, the following items: (1) Long-term placebo-controlled trials of vaccine candidates, where the placebo group remains untreated. All-cause mortality studies could then be conducted. (2) Suitable animal model systems that accurately recapitulate the disease. (3) Understanding the effects of the vaccines in unhealthy people or those with underlying conditions. (4) Ensuring that the mRNA stays intracellularly and does not enter the extracellular space.
• Better affordability. Once they are no longer covered by OWS, the ~$110 a dose that is projected for the mRNA vaccines may prove more costly than COVID-19 vaccines made by other technologies.
• Resolution of safety issues.
• Improvement in immune response duration and the ability to prevent infection and transmission.

In their current iteration, the COVID-19 mRNA vaccines will most likely continue to be available under emergency use authorization (EUA) but are unlikely to be able to meet the much more stringent requirements needed for manufacture under a biologics license application (BLA). Until then, the curtains may soon close on Act 1 of the mRNA vaccines.

As it was once said, “The first horse out of the gate isn’t necessarily Secretariat.” (Savio Woo ca, 2004).

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