A full slate of COVID-19 vaccine candidates — what it will take to win in a crowded field
My idea of a good weekend used to be holing up with my favorite recipes and podcasts. Now I can’t wait for a COVID-19 vaccine, so I can be unleashed on the world. But wait we must. Let me explain why.
Therapies and preventives like vaccines need to go through an extensive regulatory process. Each entrant, called a candidate, must complete a series of progressively more difficult challenges, culminating in several levels of human clinical trials, to ensure that it doesn’t have serious side effects and works as intended. Only then will it be approved for the masses. This all takes time.
And when time is of the essence, it takes numbers to find one or more victors as quickly as possible. As of mid-May, there are over 100 vaccine candidates against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, in the queue.
Vaccines have been preventing disease since the 18th century. With all that history you’d think it would be simple to make a vaccine. But each virus is its own beast. For each one, scientists must figure out what type of molecule, or immunogen, will stimulate a person’s immune system to make antibodies that offer lasting protection against that specific virus. Traditionally, vaccines have used versions of the virus itself as an immunogen. For example, the hepatitis A vaccine uses inactivated virus, and the one for chickenpox uses live virus that has been attenuated, or modified, to temper its activity.
Along with these stalwarts, the slate of SARS-CoV-2 candidates boasts newcomers such as nucleic acids, including the first candidate to reach clinical trials in the US, which uses technology that has yet to be proven in prime time. The field is wide and deep with different modalities, with several other candidates following close on the frontrunner’s heels.
This is why it’s hard to develop vaccines
In addition to making sure a candidate works, or has efficacy, it must be checked for undesirable effects. For example, it’s not unusual for a live, attenuated vaccine to provoke a mild form of the viral infection, as is sometimes the case with the annual flu vaccine. But care must be taken to ensure it doesn’t instigate a full-blown infection.
We talk about this in an episode of Discovery Matters… listen here: The artistry of vaccine development.
In the episode we hear about certain negative side effects that sometimes occur. In adults versus children, such a distinction was found just over 10 years ago with the vaccine against swine flu, H1N1. The vaccine turned out to cause sudden attacks of sleep, called narcolepsy, in a small percentage of children. Notably, this distinction was only unearthed after the vaccination program was rolled out to hundreds of thousands.
After one or more SARS-CoV-2 candidates make it through this gauntlet, production needs to be scaled up, ultimately to billions of doses. This again, will take time, so a vaccine will likely be rolled out in phases with frontline healthcare professionals and high-risk people served first.
Public, private, and government agencies are collaborating, working at warp speed to pare down the timeline from the many years typical for vaccine development. Until then, we know what to do.
Resources
COVID-19 (coronavirus) vaccine: get the facts. Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-vaccine/art-20484859 Accessed May 22, 2020.
Edmond C. 3 challenges in creating a coronavirus vaccine — and how they are being overcome. World Economic Forum. https://www.weforum.org/agenda/2020/05/coronavirus-covid-19-vaccine-industry/ Accessed May 22, 2020.
Ricks D. Race for a coronavirus vaccine. Genetic Engineering & Biotechnology News. https://www.genengnews.com/insights/race-for-a-coronavirus-vaccine/ Accessed May 22, 2020.
Le TT, Andreadakis Z, Kumar A. et al. The COVID-19 development landscape. Nature Reviews Drug Discovery. https://www.nature.com/articles/d41573-020-00073-5 Accessed May 22, 2020.
