With COVID-19 vaccines being administered to our front-line health care workers and residents of long-term care facilities, we are beginning to see the light at the end of the tunnel of this pandemic. Yet, given the time-limited nature of the vaccine’s development, we have yet to learn the extent to which vaccinated people can spread the virus. The COVID-19 vaccinations prevent disease, but we know little about if it prevents reinfection and further viral transmission. In fact, vaccinated populations that act under the assumption that they are immune and therefore cannot spread the virus may prove to be the next super-spreaders.
But how can vaccinated people/populations spread the virus? As with many respiratory viruses, including the novel coronavirus, the nose is the main entry point. Here, the virus will replicate and will begin to attack the body. For those who have taken the Pfizer and Moderna vaccines, their immune systems have been “prepped” to recognize and attack the virus as soon as it is detected by the immune cells. Yet, there is still a sizeable period of time between replicating the virus and recognizing and eliminating the virus.
It is this critical period of time when the human host may continue to spread the virus to other humans. This was exhibited by the first person discovered to be reinfected with the coronavirus in Hong Kong, who spread the virus to others despite having no symptoms. Although it has been proven that the Pfizer and Moderna vaccines effectively prevent serious illness, there have been few studies indicating how they affect viral transmission.
With a slower than expected vaccination rollout to the general public, people who are vaccinated and fail to understand that they can still be carriers of the virus pose an immediate threat to the unvaccinated. To curb the spread, we need to 1) research the effectiveness of the vaccine in reducing community transmission; 2) invest in mucosal vaccines that elicit more targeted immune responses in the nasal mucosa; and, 3) educate people who are getting vaccines about how they may still be carriers of the virus.
Without examining the vaccine’s effectiveness in reducing viral spread, vaccinated populations must continue to act under the assumption that they can spread the virus to others. Although a study of COVID-19 patients suggested that a strong immune response in the blood would protect mucosal tissues, we need to continue studying how antibody levels in saliva and blood compare for vaccinated populations and how this impacts the potential for viral transmission.
Investing more resources into mucosal vaccines, such as a nasal spray, may pay dividends in the long-run. By presenting a pathogen so that the immune system naturally sees them, our bodies will be more adept at fighting the virus. Additionally, since the nose is the main port of entry, a mucosal vaccine will quickly elicit an immune response to the virus when it tries to breach the body’s barriers at the nasal cavity. This leaves it far less time to multiply inside the nasal cavity and spread to other humans, which decreases the viral load in the nose and reduces viral transmission.
As the population begins to receive the vaccination, scientists fear that social distancing measures and mask-wearing behavior will ease up. We must carefully educate a population dealing with serious virus fatigue and malaise that although receiving the vaccinations seems to prevent serious illness, we are unsure if they significantly reduce community transmission of the virus. If vaccinated populations ignore social distancing protocol and fail to wear masks, this could lead to a massive surge of cases and hospitalizations, adding to the already devastating impact of the pandemic.
As winter ends and social behavior increases in vaccinated and non-vaccinated folk, there will be yet another opportunity for a third surge. This time, it may be those who are deemed to be the least susceptible to spreading the virus spearheading the third surge.
Rushabh Doshi is a public health student.
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