American Scientist

The possibility of you or me receiving a COVID-19 vaccine gets closer by the minute. Because two of the leading companies in the research and development of COVID-19 vaccines, Pfizer/BioNTech and Moderna, just received emergency use green lights from the U.S. Food and Drug Administration (FDA), one may immediately think that wearing a mask is about to be over and long forgotten.

Vaccines are intricate components in the control of infectious diseases, and yet their effectiveness is linked to social, political, and economic aspects that go beyond the laboratories in which the inoculations were developed. Unfortunately, each of these factors can be and has been distorted to fit individual goals and biases at some point in every public health crisis—including in the current pandemic. Rampant misinformation across the internet, mixed with conflicting messages from public health authorities and the U.S. government, during an era of growing antiscience rhetoric has proven to be a recipe for disaster. Information about COVID-19 vaccines is exciting and continues to emerge, yet the risk of such vaccines giving people a false sense of security is serious. We all are ready to socialize like normal again but there are several social and epidemiological considerations about how vaccines work and how people behave that make wearing masks necessary for much longer. 

If you have seen the exciting charts from the vaccine trials by Pfizer and its partner BioNTech and Moderna, you are probably feeling as hopeful as I am. The trials concluded an efficacy of 95 percent for Pfizer’s BNT162b2 and 94 percent for Moderna’s mRNA-1273, an extraordinary outcome for both companies. The data show both vaccines provide protection after two weeks following the first shot, which matches how long it typically takes for our immune system to mount an immune response after vaccination. Does that mean that you can visit your relatives or lift your protective guidelines after vaccination, without fear of exposing them? Not necessarily.

First, and perhaps most important, right now we know that both these vaccines prevent symptomatic COVID-19. Whether they prevent infection entirely or just symptoms remains unknown. This caveat means that if the vaccines do not prevent infection entirely, someone who is vaccinated might still be able to carry and transmit the virus. As we have seen with asymptomatic cases of COVID-19, disease manifestation—the readout in vaccine efficacy trials—and transmission are not mutually exclusive. It is likely that the potential for transmission would be much lower than in an unvaccinated individual because the immune system would probably prevent high virus titers, but we still do not know for sure. Using face masks and following social distancing guidelines will be key to mitigating virus transmissibility.

Second, although the data from the vaccine trials show protection within the expected two-week period, it is likely that maximal protection may not happen until weeks after the booster, a common practice intended to yield a much stronger immune response. According to current guidelines, Pfizer’s second shot is administered 21 days after the first challenge, while Moderna’s wait for the second shot is a week longer at 28 days. Creating memories requires time and effort, and so does developing immunological memory.

Third, the vaccination protocols are asynchronous, and certain groups are not eligible to receive the vaccine. Not all of us will be vaccinated simultaneously, and children are currently not eligible to receive the COVID-19 vaccines. Without travel restrictions and enforcement of nonpharmacological interventions, for example, a vaccinated individual introducing new cases to countries without immediate vaccine accessibility is a possible scenario. We also know that, for example, there can be dramatic differences in vaccine efficacy between residents of low-income countries compared to high-income countries, as has been reported for other vaccines. These considerations must be kept in mind as we move forward and gather evidence for the level of protection and efficacy in different demographics.

Fourth, the possibility that the virus could mutate its spike protein—the part of the virus needed to enter our cells and the target of current vaccines—to escape human population immunity via the vaccines is plausible. Genetic mutations are the basis of evolution and viruses rely on them to overcome new hurdles such as population immunity. This phenomenon is demonstrated by the need to regularly update vaccines for influenza virus according to the evolution of circulating strains. Although not all viruses have been successful at escaping vaccine-derived immunity, new evidence for escape immunity in other coronavirus species, particularly in their spike protein, points at this possibility. It takes a large percent of the population to have immunity before immune-escape variants dominate and can be detected in the population. Thus, it is unlikely that this would be an issue in 2021 with the current vaccines. However, vaccine efficacy may change over time and current efforts will need to focus on maximizing the protective benefits of the current vaccines while simultaneously reducing transmission through mask-wearing.

Fifth, not everyone will get vaccinated. Whether related to general antivaccination beliefs or not, it would be foolish for us to believe that everyone in this country will be immunized. We have seen a taste of what to expect by looking at the dynamics of mask use compliance across the country and assuming a future correlation. Misconceptions that those who have previously been infected with COVID-19 do not have to take the vaccine are still flowing around the internet.

More than 300,000 lives have been lost due to COVID-19 in the United States alone as of mid-December. Although this tragic number is hard to grasp, the death toll would have been significantly higher without social distancing and face mask practices. A new report showed that limiting group gatherings and closing educational institutions as well as face-to-face businesses in early 2020 contributed to a significant reduction in viral transmission in multiple countries—reflecting what could have been in countries where these measures were not implemented or were haphazardly implemented. In contrast with initial quarantine, face mask use in the United States was not recommended by the U.S. Centers for Disease Control and Prevention (CDC) until the beginning of April when evidence for presymptomatic and asymptomatic transmission of COVID-19 started to emerge. We now have extensive evidence for masks’ effectiveness in reducing transmission of coronaviruses in multiple settings, along with the effectiveness of physical distancing. Unfortunately, the percentage of U.S. residents who are sticking to the guidelines is far from ideal. Epidemiologists have modeled and projected the lives that could be saved between now and February 2021 with various increases in mask wearing. Clearly, we all have work to do.

Currently, 38 U.S. states are now mandating face coverings in public, and even more stringent regulations are on the horizon in some of these states. But this precaution is far from enough. The effectiveness of wearing face masks has been heavily scrutinized and even politicized since the practice was originally recommended and subsequently enforced. The tug-of-war–like dynamics between mask-use compliance and their rebuttal have implicitly divided the country in ways we had not anticipated.

Scientists and media outlets now more than ever have the responsibility to ensure that such key messages are accessible, transparent, and understood by the public. Nonetheless, these efforts can only go so far. Early in July—while the number of COVID-19 cases in the United States was on a rise—we saw mask-wearing mandates being lifted by local governments, acts that diminished public trust in science. As we approach the end of 2020, a dozen states continue to refrain from enforcing tighter public health regulations amid a nationwide crisis. The research and development of hope originated in laboratories; now the challenge lies in the effective communication and action between all parties involved and, for a global health threat, that means everyone. The outcome of this pandemic will continue to rely on the continuous implementation and enforcement of mask use and social distancing guidelines for some time, even after you and I are vaccinated.