The coming availability of a vaccine for COVID-19 has prompted considerable excitement – and concern – about the speed with which new medical technology has become available.
But while the COVID-19 vaccine itself is new, vaccines in general are an ancient method of rallying the human body's natural defenses against disease. And the vaccine for a coronavirus was actually in the works behind the scenes for some years, giving us more time than meets the eye to understand how this technology works, whether it is safe, and who should consider getting the vaccine.
Historical evidence suggests the Chinese began using rudimentary vaccines to prevent smallpox as early as 1000 CE, according to The College of Physicians of Philadelphia. Ancient physicians would inoculate patients against the disease by collecting the scabs of patients who had recently recovered from smallpox, grinding the scabs, and blowing them up a healthy individual's nose. The receiving patient would become permanently immune to the disease. These techniques traveled across the Middle East, Africa, and reached Europe by the 1700s.
The COVID-19 vaccines currently en route to Utah hospitals contain cutting-edge technologies that represent the culmination of years of scientific research, according to Dr. Audrey Stevenson, director of Salt Lake County Health Department's division of family health. This technology may not only help to end our current pandemic, but may also hold the key to combating a whole range of medical conditions – like HIV, allergies and maybe even cancer.
So how does it work, and how is it different from your annual flu shot? It all boils down to how the vaccine itself is made.
All vaccines work with our natural immune systems to prevent disease, Stevenson explains. Certain cells within the human body serve as microscopic security guards, seeking out and destroying disease-causing viruses, bacteria and other unwanted intruders. But in order to stop a disease, these cells have to learn to recognize the agent that causes it as unwelcome.
Viruses, and the virus that causes COVID-19 in particular, are especially difficult for the immune system to recognize. Viruses are incapable of reproducing by themselves. In order to make copies of themselves, viruses trick our cells into letting the virus inside. Once there, they take control of the cell and turn it into a virus factory.
When we survive infection by a virus, our immune cells remember the virus that caused the attack. The next time we encounter that same virus, the immune system responds quickly, destroying the virus before it enters too many of our cells and causes us to get sick.
Vaccines take advantage of this natural process by teaching our immune system to recognize a viral intruder before we catch the disease. Traditionally, this is done by injecting a very small amount of the virus itself. The virus is often weakened or, in some cases, killed entirely so that it can't spread and cause disease inside the body while the immune system learns to recognize it.
However, some viruses are especially tricky to prevent with vaccines. COVID-19 is a master of disguise that uses what scientists have named a “spike protein” to enter our cells, according to Tamara Sheffield, Director of Community Health and Prevention at Intermountain Healthcare. The spike protein acts kind of like a key, which unlocks the cell and lets the virus inside so it can reproduce and cause disease and, for some people, severe illness.
“The problem with this disease is we're finding it causes these inflammatory reactions that can cause permanent damage to the lungs and cardiovascular systems,” Stevenson said. “It's not a benign disease. Some go on to have chronic conditions.”
Because of the spike protein, our bodies have a particularly difficult time stopping COVID-19 and other viruses from the coronavirus family. And, injecting people with COVID-19 doesn't trigger immunity. So scientists had to consider a different approach, but they weren't starting from scratch.
Coronaviruses have been monitored as a potential threat to public health since the 1960s, Stevenson said. The SARS outbreaks of the early 2000s, caused by a COVID-19 sister virus identified as SARS-CoV-1, prompted scientists to begin developing a coronavirus vaccine. Although work on that vaccine slowed when SARS settled down, Stevenson said research tied to the SARS outbreak and other coronaviruses meant scientists had a head start on the development of a vaccine for COVID-19.
“Despite how quickly the vaccine technology has been [developed],” Stevenson said, “there really have not been any shortcuts with regard to determining the safety of this vaccine.”
This early research also helped scientists zero in on which of many new vaccine technologies might combat COVID-19 and its spike protein. The first vaccines to come online, developed by Pfizer and Moderna, contain a form of genetic material called “messenger” RNA. This mRNA is a natural substance similar to, but not exactly the same as, DNA. Messenger RNA tells the cell how to make proteins that do the work in a cell.
On Dec. 11, the U.S. Food and Drug Administration determined the Pfizer vaccine is safe and effective in individuals ages 16 and older. The mRNA in the Pfizer vaccine instructs cells to make copies of the COVID-19 spike protein, which teaches the immune system to defend itself against the virus without causing illness.
There are both advantages and disadvantages to this vaccine approach. On the upside, data from the Pfizer and Moderna trials suggest that mRNA vaccines are incredibly effective, reducing the risk of getting COVID-19 by nearly 95%. The flu shot, by comparison, reduces the risk of disease by roughly 40-60%, according to the Centers for Disease Control and Prevention.
The flip side of this efficacy is that the mRNA vaccine triggers a noticeably aggressive response from our immune system. That is, some people who have had the vaccine experienced side effects including fever, chills, headache and body aches. These symptoms reportedly last 24-48 hours in most people, and are unlikely to cause hospitalization, disability or death, Stevenson said.
Medical workers who receive the vaccine in the coming weeks will take each dose toward the end of their shifts to give them time to recover from any side effects. However, people who experience these symptoms do not need to quarantine – they can continue with their daily activities as soon as they like.
“With all vaccines, what we study in tens of thousands of people gives us a good idea of basic safety,” said Dr. Andrew Pavia, head of the Division of Pediatric Infectious Diseases at the UofU, “but that doesn't tell us what could happen in rare instances. The COVID-19 virus [is estimated to] kill 1 in 150 people [who contract the virus]. What we don't know about the vaccine is whether there might be a side effect that affects one in a half million people.”
According to the FDA, symptoms are more likely to occur after the second dose of the vaccine than after the first. However, people who do not get the necessary second dose three weeks after the first injection may not have a sufficiently strong immune response to prevent infection. It's important for people to remember what brand of vaccine they received – Pfizer, Moderna or another vaccine – Stevenson said. The vaccines are not interchangeable and patients will not develop full immunity to the virus if they do not get two doses from the same manufacturer.
Because the vaccine has been available, even in trial settings, for less than a year, it's also unclear how long the immunity granted by the vaccine will last. “There will be ongoing studies that look at vaccine effectiveness over time,” Pavia said.
For this reason – and because it takes some time for the vaccine to take full effect – people who receive the vaccine will still have to take precautionary steps such as handwashing and wearing a mask to prevent the spread of COVID-19, Sheffield said. Masks are also necessary to stop the virus from spreading among people who have not yet had access to the vaccine, Stevenson said, which could take some time due to the unique nature of the vaccine, which is extremely fragile.
The first doses of the vaccine will be distributed to employees of Utah's largest hospitals, which are equipped with special freezers to store the vaccine at less than negative 80 degrees Celsius, according to Jeanmarie Mayer, an epidemiologist for University of Utah Health Hospitals and Clinics. Giving the vaccine to healthcare workers first will also help to ensure there are adequate doctors, nurses and other medical staff available to care for patients as the pandemic continues, according to R. Alta Charo, a professor of law and bioethics at the University of Madison Wisconsin.
After healthcare workers are vaccinated, Sheffield said, Utah medical providers will work to increase the availability of the vaccine as fast as possible, making it first available to the state's essential workers, then to adults over age 65. The vaccine is expected to be available to the majority of adults, at little or no cost, by next summer, she said.