How do we know if the COVID-19 vaccines are working?

COVID-19 vaccines can keep people safe and move our country closer to herd immunity. This means that widespread immunization is a public health race that has immense economic and social consequences. 

One bright light is the number of new COVID-19 cases has fallen precipitously over the past two weeks, with sub-100,000 new case days now the norm. One can hypothesize why this sudden drop has occurred, but no one knows with certainty the reason.    

Is this the lull before the next storm? Will college students take trips in March even if colleges do away with Spring break? Will March Madness stir virus transmission among rabid fans gathering to watch the games? Will family gatherings for Easter in April spawn a new surge of infections?  

The vaccines are in a race with the virus, each scrambling to reach each person first. Three distinct groups will indicate whether the vaccine is winning its race with the virus.    

Airport security checkpoints

Even with face covering and face shield precautions, over 6,800 Transportation Security Administration (TSA) officers have tested positive and 15 have died from COVID-19 over the past year. This means that 15 percent of the TSA airport security workforce have been infected. As more TSA officers and air travelers are vaccinated, the number of new infections among TSA officers should begin to drop — a sign that the vaccine is reaching such people and providing protection.     

Senior Citizens

We all know that those over 65 years old have been hardest hit by COVID-19. They represent 14 percent of all confirmed cases, yet over 80 percent of all reported deaths. Soon, all such people will be fully immunized. Given their fatality risk, this group will lead the drop in the nation’s death toll, indicating the benefit of the vaccine. Moreover, such a drop will be evidence of the effectiveness of the vaccines in this vulnerable population in practice, not just what was observed during clinical trials.  

Young Adults

Those who are 18 to 29 years old, including college students, have had more infections than any other age group. This group is also last on the priority list for COVID-19 vaccines. Although they have not experienced a high rate of poor outcomes, they keep the virus alive by spreading it, allowing it to mutate into new variants. When the number of new infections in this age group begins to fall, this will be a sign that we are moving closer to herd immunity, with the influence of the vaccine on higher risk groups shrinking the pool of people in the population susceptible to infection.  

Many are looking forward to warmer weather and opportunities to gather, hoping that widespread vaccination will bring the nation closer to herd immunity. The big unknown is the effectiveness of the COVID-19 vaccines in the general population. Even at herd immunity, isolated pockets of outbreaks will continue to emerge. This means that the development of safe and effective treatments must become the next priority for the Biden administration. In addition, new variants of the virus may require tweaks to the existing vaccines, leading to the need for COVID-19 booster shots in the future.   

The arrival of COVID-19 vaccines does not mean that we are ending our battle with COVID-19. Quite the contrary — we are now firmly entrenched in adapting our lives to a world with COVID-19 risk. Vaccines and treatments are stepping stones in our nation’s race against the virus — a race that must be won if we are to return to the people and activities we sorely miss. This is no tortoise versus hare race. This is a race for our lives and our livelihoods.            

Sheldon H. Jacobson, PhD, is a Founder professor of Computer Science at the University of Illinois at Urbana-Champaign. He applies his expertise in data-driven risk-based assessment to evaluate and inform public policy and public health. He served as a member of the National Academy of Medicine standing committee for the Strategic National Stockpile in 2015-2017.         

Janet A. Jokela, MD, MPH, is the acting regional dean of the University of Illinois College of Medicine at Urbana-Champaign, and an internal medicine and infectious disease physician. She is a graduate of the University of Minnesota Medical School and trained in internal medicine at Boston City Hospital and infectious diseases at Harvard.