The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the ongoing coronavirus disease 2019 (COVID-19) pandemic that has taken over five million lives. Since it spreads via respiratory droplets and aerosols, causing asymptomatic or mild infection in most cases, physical distancing and face protection is paramount when it comes to interrupting transmission, even with vaccination.
Study: Ranking the Effectiveness of Non-Pharmaceutical Interventions to Counter COVID-19 in UK Universities with Vaccinated Population. Image Credit: BGStock72/ Shutterstock
A new paper describes the effects of various non-pharmaceutical interventions (NPIs) in dealing with the spread of this virus among students, faculty, and staff on university campuses following the reopening of these institutions.
Vaccination has been carried out on a mass scale in many countries, but coverage is seldom more than 70-80% of the total population. Moreover, breakthrough infections have occurred in many vaccinated individuals, aided by the emergence of newer variants of concern, including the Alpha, Beta, Gamma, and Delta.
The Delta variant has stimulated the resurgence of the virus in many places on different continents, with dramatically increased transmissibility compared to the wildtype variant and partial escape from host immunity. Coupled with a decay of host immunity elicited by vaccination, this has led to the fear that vaccines may not protect against the virus over time.
In other words, NPIs continue to play a vital role in containing the virus transmission. The current paper, which appeared on the medRxiv* preprint server, examines the impact of NPIs currently being implemented in combination in the British universities that have opened up again. These institutions have a two-fold aim: to promote student activities on campus as far as possible while preventing viral transmission.
Universities are not general settings but have their own microenvironment due to their composition of students and staff and their dual aims, as given above. The people on campus interact to different degrees and have different rates of serious disease and vaccination. The current study thus aims to model a safe template for on-campus activity and identify the most effective NPIs in terms of achieving safe campus interactions.
The study is built on a compartmental model, commonly used in COVID-19 research. Unlike many earlier models that depend on changing the parameters of the model to understand how different prevention and control measures would influence the outcome, here the authors used this model to explore the spread of the virus in universities and the role of NPIs in curbing it.
Called a double SEIQR structure, this model views the stages of spread among students and staff discretely, such as susceptible (including the vaccinated), exposed or asymptomatic, infected or symptomatic, quarantined (including the isolated and hospitalized), and recovered. The concentration of the virus in the environment shared by students and staff, who follow similar routines, is also considered here.
Asymptomatic isolation is unlikely on campus and is not included, but vaccine breakthrough infections are modeled. Reinfection is excluded, and deaths among vaccinated individuals.
Potential NPIs include mask use, social distancing, disinfection of the environment, and the quarantine of infected students and staff. In the minimum-case scenario, the NPIs are implemented at the maximum level, while in the minimum-intervention scenario, the attempt is to remove as many control measures as possible. This can be either with or without the use of quarantines.
The trends in case numbers are compared with each scenario to identify the most effective combination in each case.
What did the study show?
The study results show that NPIs have varying values related mathematically to the stage of the epidemic. For instance, with a student strength of 1,200 students per university department, and 150 staff, the vaccination rate is pegged at 68% and 79%, respectively.
At baseline (no interventions), they found that the effective reproduction number R0 at the outset is 1:40, with five asymptomatic cases among the students and two among the staff. This grows to an outbreak over the coming weeks, before tapering out at about 250 days, in the example given above.
By this time, almost 60% of students and 70% of staff are infected, showing that this scenario is not optimal; rather, NPIs are needed.
With the minimum intervention scenario, and when quarantine is minimized, again, 94% of the staff and students are not infected. Mask wearing is the most effective intervention, followed by social distancing. With both these measures in place, far less environmental disinfection is required. Their importance is obvious since close contact is unavoidable in a university.
When non-quarantine interventions are little used, the main intervention is quarantine, allowing the susceptible population to be protected against infection. Mandatory quarantine of symptomatic students, compared to that of staff, has greater importance for reducing the rates of infections.
What are the implications?
These results show that for optimal on-campus interactions with minimal interventions, mask-wearing and social distancing are to be stressed, especially among students. Infected students must be identified and quarantined to protect the rest of the population against viral spread.
This model can be adapted to study other outcomes or parameters, thus helping to predict the course of the outbreak and manage it. The study shows how important it is to use a range of NPIs to balance on-campus teaching with limited viral transmission, especially when there is a perceived need to increase student activity on campuses.
The study also shows how little is known about the small environments like businesses and schools that cannot be dealt with using the tools of general epidemiology due to their unique profile of population composition, symptoms, vaccination rates, and interactions. Customized tools must be used to identify the optimal interventions required to keep the campus humming smoothly while preventing a large outbreak.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.