The latest data on COVID-19 vaccine effectiveness is in, and it is mostly good news. The vaccines continue to be highly effective at preventing severe illness and hospitalization, with no significant decline in effectiveness (at preventing hospitalization) so far. In addition, the majority of COVID cases, and almost all severe cases of COVID that require hospitalization, are occurring in unvaccinated individuals. Vaccination remains the best protection against COVID-19, and especially against severe cases of the disease that require hospitalization.
There is, however, a decline in effectiveness of the vaccines over time in preventing mild or asymptomatic cases of COVID-19. There are likely two reasons for this decline, both of which were expected. First, immune protection tends to decline over time for many diseases, which is why periodic booster shots are often needed. Second, the persistence of the epidemic means that new variants continue to evolve, and the vaccines to date provide less protection against some of these (like the Delta variant of the virus).
Vaccination for fast-evolving viruses like the one that causes COVID-19 rarely provide 100% protection. This is why we need a new flu vaccine every year. As new viral variants appear and begin to circulate in the global population, new vaccines must be developed to prevent new flu epidemics.
Because many people remain unvaccinated, Texas (and most of the country) is experiencing a new wave of COVID-19 infections. Once again, intensive care units of hospitals are stressed. Almost all the hospitalized patients are unvaccinated, although the surge in infections means a greater risk (especially of relatively mild cases) for vaccinated individuals as well. Masking in public (especially in crowded places), frequent hand-washing, and social distancing are the most effective ways to further reduce your chances of infection, even if you are fully vaccinated.
In Mason County, most people have been vaccinated with either the Moderna or Pfizer vaccines, which are very similar in their mode of action. These vaccines are administered in two doses. The second dose greatly increases the immune response, and provides both more effective and more lasting protection. In two-dose vaccines like these, there is a trade-off in the timing of the second dose. A longer wait between doses provides a stronger immune response to the second dose. However, a longer wait also leaves the vaccinated person more vulnerable for a longer time.
Booster shots, given months (or even years, for some vaccines) after the initial vaccinations, can provide much higher levels of immune protection. In addition, booster shots can provide protection against newly emerging variants of the virus. Booster shots for the Moderna and Pfizer vaccines have now been developed, and it is likely that they will soon be recommended for people at about 8 months after the second initial dose.
There is some controversy among health officials over the booster shots, but it has nothing to do with their effectiveness. The booster is clearly highly effective and safe, and individuals who receive a booster will certainly be protected at a much higher level against COVID-19. The reason that the booster shots are controversial is that some people argue that we need to be putting available resources into getting initial vaccination for most of the world’s population. Although the vaccines are widely available in the United States, the same is not true of many other countries, and only about 31% of the world’s population is currently vaccinated. This means that the epidemic will continue, and new variants will continue to emerge, which could impact both vaccinated and unvaccinated individuals everywhere (although unvaccinated individuals will be at far greater risk of serious illness). Therefore, one argument is that we should put our available resources into getting an initial vaccination for most of the world’s population, before emphasizing booster shots for people who are largely protected against serious disease.
On the other hand, a proactive approach to booster shots will certainly provide those who receive them with greater protection against COVID-19. For this reason, many people in the United States are already getting a booster shot (about one million have been administered so far). It appears that the booster shots will soon be recommended for everyone who has been previously vaccinated, but especially for the groups that are most at-risk for COVID-19.
Remember that taking basic steps to reduce exposure is still important as well. Frequent hand-washing, social distancing, and wearing masks in public places all reduce your chances of exposure and infection. If you are fully vaccinated and observe these basic steps for increased protection, the chances of severe disease and hospitalization can be enormously reduced.
—Have a question about science, especially as it relates to Mason County? E-mail me at dhillis@austin.utexas.edu and I will do my best to answer it in this column.
—David Hillis is the Alfred Roark Centennial Professor in Natural Sciences at the University of Texas at Austin, where he directs the Biodiversity Center. He also owns and operates the Double Helix Ranch in Mason County, where he lives.
