Dear Doctor: I don’t think I’m the only one wondering how the new coronavirus vaccines got developed so fast when other vaccines in the past took so much longer. Can you please explain?
Dear Reader: When the quest for a safe and effective coronavirus vaccine began, early in 2020, we had only previous vaccine development to guide our expectations. And you’re correct, those vaccines -- against diseases such as polio, measles, smallpox and chickenpox -- took years, or even decades, to develop.
Until now, the fastest timeline was the four years it took to develop the mumps vaccine. Yet less than a year into the current effort, two highly effective preparations have received emergency-use approval from the Food and Drug Administration. This is due to multiple factors. A crucial one is international cooperation, which resulted in the immediate sharing of the genetic sequence of this never-before-seen virus. Additionally, the global health crisis prompted abundant funding.
But perhaps most important was the nature of the virus itself. Coronaviruses get their name from the distinctive “crown” of club-shaped spike proteins on their outer surface. Thanks to years of previous research, we know that the virus uses these proteins to enter human cells. Also immensely helpful was the fact that COVID-19 is quite similar to SARS and MERS, each of them coronaviruses that also originated in animals and jumped to humans. In developing the new coronavirus vaccines, scientists were building on an existing body of knowledge.
Unlike previous vaccines, which used a weakened or inactivated virus to trigger an immune response, the new vaccines harness the molecular building blocks of the novel coronavirus. Specifically, they use a single strand of genetic code known as messenger RNA, or mRNA. The genetic code teaches human cells to build a harmless fragment of the spike protein, just enough for the immune system to recognize the coronavirus. This triggers a robust response that deactivates the spike protein. Because that spike protein is how the coronavirus penetrates a cell, disabling it prevents infection. And, because there are multiple ways to deploy mRNA, multiple vaccines are now in different stages of development. That’s also why, when you get the first of the two-dose vaccine regimen, you have to follow up with the same vaccine. You can’t mix and match.
Both approved vaccines have impressive efficacy of 94% to 95%. The numbers are a bit lower for people 65 and older, but it’s believed that may reflect the smaller sample size of clinical trial volunteers in that age group. As with many vaccines, this one has several side effects. Some people receiving the shots report experiencing pain at the injection site, headache, fatigue, pain in the muscles or joints, chills and mild fever. Several people have experienced severe reactions to the vaccine, but those cases were rare.
These new coronavirus vaccines are game-changers. In light of the dangers posed by COVID-19, as well as the lingering effects of the illness, we hope that when the vaccine becomes available to you, you will choose to get immunized.
(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
