COVID-19 vaccine

Lore & Background

COVID‑19 vaccines were developed using both classical technologies (inactivated virus or protein subunit) and novel platforms (mRNA or viral vector-based). Major vaccines include the Pfizer–BioNTech mRNA vaccine, Moderna mRNA vaccine, and the Novavax protein subunit vaccine. With the emergence of new SARS-CoV-2 variants, original vaccines have been updated as 'variant-adapted' booster doses. Common side effects include soreness, fatigue, headache, myalgia, and arthralgia, which resolve within a few days. Vaccination is safe for people who are pregnant or breastfeeding.

Reader's Guide

COVID‑19 vaccines are widely credited for reducing the spread of COVID‑19 and reducing severity and death. The Journal of Paediatrics and Child Health estimated that between 14.4 and 19.8 million deaths were prevented by the vaccine. Many countries implemented phased distribution plans prioritizing those at highest risk, such as the elderly and healthcare workers. The vaccines represent a historic achievement in rapid vaccine development, leveraging prior coronavirus research and novel mRNA technology. Their legacy includes demonstrating the feasibility of mRNA platforms for future pandemics and the importance of booster doses to maintain protection against evolving variants.

Did You Know?

• Between 14.4 and 19.8 million deaths were estimated to have been prevented by COVID‑19 vaccines.

The 1960s Disaster and Its Long Shadow

In the 1960s, scientists made their first serious attempt to create an RSV vaccine by treating the virus with formalin, producing what became known as the formalin-inactivated RSV vaccine. The results were catastrophic. Rather than protecting children, the vaccine triggered a phenomenon called vaccine-associated enhanced respiratory disease. Infants who had never encountered RSV before were vaccinated and then, upon their first natural exposure to the virus, developed far more severe illness than unvaccinated peers. They suffered fever, persistent wheezing, and bronchopneumonia. Roughly eighty percent of these children required hospitalization, compared with only five percent of virus-exposed controls who had not received the shot. Tragically, two children died from lethal lung inflammation during that first natural infection. This devastating failure cast a long shadow over the field, stalling meaningful progress in RSV vaccine research for decades and instilling a deep caution in the scientific community about how the immune system could be inadvertently primed to overreact to a respiratory pathogen.

The F Protein Breakthrough

For decades after the 1960s disaster, RSV vaccine research advanced slowly, with periodic reviews in 1998 and 2019 noting meaningful progress over each preceding decade. By 2019, more than thirty vaccine candidates existed across multiple platforms, including particle-based, attenuated, mRNA, protein subunit, and vector-based approaches, and researchers predicted a viable product within a decade. The true turning point came from a 2013 study that mapped the crystal structure of the RSV fusion protein, the F protein, and demonstrated how its structural stability could be enhanced. This insight became the foundation for identifying the most immunogenic F protein constructs. Pfizer, for example, engineered four hundred distinct F protein variants to pinpoint the ones that generated the strongest immune response, ultimately assembling a bivalent prefusion F investigational vaccine. The 2013 structural work effectively unlocked the molecular key that the field had been missing for over fifty years, transforming RSV from a seemingly intractable target into one with a clear, rational path toward a safe and effective immunization.

A Remarkably Compressed Approval Timeline

The path from published phase III data to global regulatory approval was strikingly fast. In February 2023, results from a trial involving approximately twenty-five thousand adults aged sixty and older were released, showing that a single dose of GSK's Arexvy delivered ninety-four percent efficacy against severe RSV pneumonia and seventy-two percent against broader acute respiratory infection. An FDA advisory panel endorsed approval that same month, and the European Medicines Agency followed with its own recommendation in April. By May 2023, Arexvy became the first RSV vaccine cleared by the FDA, and it received EU authorization in June. Pfizer's Abrysvo gained a unanimous FDA panel recommendation for pregnant women in May 2023. Moderna's mRNA vaccine, Mresvia, was approved in the United States in May 2024 and authorized in the EU by August of that year. Additional approvals continued into late 2024, extending coverage to younger adults at elevated risk. What had taken over sixty years of research culminated in a matter of months of regulatory action.

Global Burden and Lasting Influence

RSV remains one of the most consequential respiratory pathogens worldwide, affecting an estimated sixty-four million people and claiming roughly one hundred and sixty thousand lives each year. The vaccines developed to combat it have been recognized with a place on the World Health Organization's List of Essential Medicines, underscoring their importance to global public health. In the United States, the CDC updated its guidance in June 2024, recommending vaccination for all adults seventy-five and older, and for those aged sixty to seventy-four who carry chronic lung or heart conditions or reside in nursing homes. Pfizer's Abrysvo extends protection to pregnant individuals between thirty-two and thirty-six weeks of gestation, shielding newborns from severe disease during their first six months of life—a critical window given the challenges posed by immature infant immune systems and circulating maternal antibodies. Beyond its direct impact, the decades of RSV vaccine research provided foundational knowledge and technical expertise that accelerated the development of COVID-19 vaccines, demonstrating how persistence in tackling one pathogen can yield dividends across the entire field of infectious disease prevention.