What can wastewater tell us about vaccine effectiveness?

October 31, 2023

This respiratory season, there are now vaccines available for COVID-19, influenza, and RSV. As vaccination expands across the US, the ability to monitor virus concentrations in sewage in parallel with vaccine rollout – along with reported cases and hospitalizations – can provide real-world evidence for, and improve our understanding of, the impact of vaccination on reducing the spread of these respiratory pathogens.

Monitoring wastewater data provides invaluable insight. SARS-CoV-2, influenza virus, and RSV are shed in the stool and urine of infected individuals and aggregated in public sewers, where it can be detected and quantified to provide information on population-level 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. By monitoring influenza and RSV in wastewater, we can now assess community transmission of all three major respiratory pathogens, and develop an understanding of how vaccination may influence their transmission. 

COVID-19 and influenza vaccines are available to people of all ages, and RSV vaccines are available for those over 60 years old. The vaccines for all three of these pathogens have had high efficacy in preventing hospitalization and severe disease, representing real scientific breakthroughs.

While the high efficacy results demonstrate protection against severe symptoms at the individual level, vaccines that also prevent transmission can significantly reduce community disease burden. Research has shown that vaccination and boosters reduce infectiousness and transmission of SARS-CoV-2, including in individuals who have symptomatic breakthrough infections. The influenza vaccine has also been shown to reduce infection risk among those who are vaccinated. More research is needed to understand if RSV vaccines reduce transmission. 

With the rollout of new SARS-CoV-2 boosters, influenza, and RSV vaccines, wastewater might provide some insight on their effectiveness. Will virus circulation in communities’ wastewater remain elevated despite new vaccines and boosters? Such a result could indicate silent spread of these viruses despite effective disease suppression. Will virus concentration in sewage in fact decrease as vaccine and booster uptake increase? 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 SARS-CoV-2, influenza, and RSV — either from the vaccines or from natural infections. Therefore, it’s important to remain vigilant for transmission even after the respiratory season has passed. And testing wastewater at the community-level could be used as an early warning system for resurgence of transmission or an early start to the respiratory season.

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 these viruses. We should leverage the data trove sitting beneath our feet and be proactive in our sustained response to COVID-19, influenza, and RSV.

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, influenza, and RSV transmission.

Written by Marisa Donnelly

Dr. Marisa Donnelly, an infectious disease and public health epidemiologist at Biobot, formerly served as a CDC Epidemic Intelligence Service Officer and as a Lieutenant in the US Public Health Service, stationed at the California Department of Public Health. Her areas of expertise include emerging health threats, outbreak investigation, risk communication, and public health surveillance.