As vaccination expands across the US, the ability to monitor the virus concentration in sewage in parallel with vaccine rollout and reported Covid-19 cases can provide real-world evidence for, and improve our understanding of, the impact of vaccination on reducing the spread of Covid-19.
Monitoring wastewater data provides invaluable insight. The SARS-CoV-2 virus is shed in the stool of infected individuals and aggregated in public sewers, where it can be detected and quantified to provide information on population-level Covid-19 incidence. Since the beginning of the pandemic, wastewater analysis has emerged as a promising technology to assess community transmission of Covid-19 and monitor its spread in near real-time.
Both vaccines authorized by the FDA had high efficacy results in clinical trials (>94%) in protecting against symptomatic disease of Covid-19, exceeding expectations and representing a real scientific breakthrough.
While the high efficacy results demonstrate protection against severe symptoms at the individual level, vaccines also need to prevent transmission to effectively halt the pandemic. The efficacy of vaccines in preventing transmission was not thoroughly investigated in either vaccine trial. It’s very likely that these vaccines will also reduce transmission and prevent asymptomatic infection, but we need to wait some time before we have conclusive evidence.
While we wait for more data from ongoing clinical trials on transmission, wastewater might provide some insight. Will virus circulation in communities’ wastewater remain elevated despite vaccination programs? Such a result could indicate silent spread of the virus despite effective disease suppression. Will virus concentration in sewage in fact decrease as vaccine uptake increases? Such a result could indicate an effect of vaccination on overall virus transmission.
Another important unanswered question concerns the duration of immunity protection against infection by the novel coronavirus — either from the vaccine or from natural infection. Therefore, it’s important to remain vigilant for Covid-19 re-emergence even after the pandemic has passed. And testing wastewater at the community-level could be used as an early warning system for resurgence of Covid-19.
Monitoring wastewater for reintroduction of viruses — sometimes referred to as environmental surveillance — has been widely applied in the successful quest to eradicate polio around the world. In Israel in 2013, researchers detected an outbreak of poliovirus through their wastewater surveillance program before any local clinics reported symptoms. Armed with this information, the government responded swiftly with targeted vaccination efforts that effectively contained the outbreak.
Vaccines are one of our most powerful tools against infectious diseases, and the extraordinary efforts behind the current vaccine development should not be understated. But vaccine roll out is complex and it will take time for vaccination to have an impact at the population level.
In the meantime, we must remain vigilant and use every tool at our disposal to prevent transmission of the virus. We should leverage the data trove sitting beneath our feet and be proactive in our sustained response to Covid-19.
As a cost-effective and non-invasive method of testing the population at scale, wastewater monitoring can provide snapshots of virus spread and serve as a sentinel for Covid-19 resurgence.
Written by Nour Sharara, MPH
Nour is a Public Health Specialist at Biobot and has been working at the intersection of Epidemic Preparedness and Response, Vaccine Equity and Global Health for over 5 years.