Publication date: Jun 22, 2020
To meet such a tight deadline, scientists are trying new vaccine technologies under development for years, but have rarely or never been used in large numbers of people.
Here are explanations of each of the major technologies, and a few pros and cons, compiled with help from several experts, including Scott Weaver, director of the Institute for Human Infections Immunity and Scientific Director of the Galveston National Laboratory, in Texas: Whole virus vaccine: Live-attenuated Strengths: Live-attenuated whole virus vaccines are the powerhouses of the vaccine arsenal.
One dose of the MMR vaccine is 93% effective against measles, 78% effective against mumps, and 97% effective against rubella, according to the U. S. Centers for Disease Control and Prevention.
Whole virus vaccine: Killed Strengths: The killed form of whole virus vaccines is considered very effective, as well as safe, because it cannot cause the illness it is designed to protect against.
The polio and rabies vaccines, among others, use a killed version of the virus itself to spur the immune system into action.
The same thing happened in the mid-1960s with a killed measles virus vaccine, said Paul Offit, who directs the Vaccine Education Center at The Children’s Hospital of Philadelphia.
They used something other than formaldehyde to kill the virus used in their candidate vaccine.
These vaccines are relatively easy to manufacture, safe and proven to provide immune responses, said Dr. Larry Schlesinger, CEO and president of Texas Biomedical Research Institute.
Weaknesses: To be effective, this vaccine may need to be paired with an immune stimulant, which can cause side effects, Weaver said.
It’s not clear how long an immune response to SARS-CoV-2 from a protein-based vaccine will last, Schlesinger said.
Viral vector vaccines Strengths: Viruses are great at invading cells and using their machinery to make more copies of themselves.
These vaccines can spur a strong immune response, meaning they’re likely to be effective, Weaver said.
Weaknesses: With the Ebola vaccine, which relies on the vesicular stomatitis virus, people get a mild, flu-like illness and are “not feeling too great for a couple of days,” Weaver said.
Nucleic acid vaccines Strengths: There’s a lot of excitement in the vaccine development world around a new type of vaccine based on delivering strands of genetic material – essentially an instruction manual to turn people’s cells into spike protein factories.
Moderna’s candidate vaccine, called mRNA-1273, was ready to be tested in people just 63 days after the virus’ genetic sequence was made public in January.
Weaknesses: This novel approach to vaccine development has never been tried before in large numbers of people, so there are lots of open questions about its safety and effectiveness.