Vaccines once took years; COVID-19 shots arrived in months after decades of groundwork
No vaccine for an infectious disease had ever been produced in under several years, and no human coronavirus vaccine existed at all. Yet COVID-19 trials began in March 2020, and by August 2024 more than 13 billion doses had been given worldwide, built on mRNA research that later won a Nobel Prize.
The speed rested on earlier work. Scientists had spent years chasing vaccines against SARS and MERS, two dangerous coronaviruses; candidates were tested in animals, and by March 2020 one DNA-based MERS vaccine had cleared a first human safety trial. Veterinarians already had coronavirus vaccines for chickens, dogs and cats. Crucially, Katalin Karikó and Drew Weissman had been developing messenger RNA as a medical tool for decades, testing it in mice, and Moderna began human trials of an mRNA vaccine in 2015. Egg-grown vaccines typically need over a decade; mRNA can be manufactured quickly. Viral vector technology, previously cleared for Ebola, offered another fast route.
Regulators did not skip the usual three trial phases; they ran them in parallel. Developers pursued both classic designs, using inactivated virus or protein pieces, and new platforms. Most target the spike protein, which the virus uses to enter cells and which provokes a strong immune response. By July 2021 at least nine technology platforms were in development. Most early vaccines needed two doses, though Janssen's and Convidecia used one.
Distribution exposed global inequality. By December 2020 more than 10 billion doses had been preordered, and about half went to high-income countries holding 14 percent of the world's population. Many nations vaccinated the elderly and healthcare workers first. One estimate in the Journal of Paediatrics and Child Health put deaths prevented at between 14.4 and 19.8 million.
Protection fades with time, and new variants prompted updated versions of the Pfizer-BioNTech and Moderna shots, offered as boosters. Typical side effects such as a sore arm, tiredness, headache and aching muscles or joints clear on their own within a few days. In 2023 Karikó and Weissman shared the Nobel Prize in Physiology or Medicine, honouring their mRNA work.
Source: COVID-19 vaccine
