Contact Tracing’s Effectiveness on COVID-19 Examined

Contact tracing mitigates the spread of COVID-19 but proves more effective against the original strains of the disease than the Delta variant. Extra effort must be applied to properly conduct contact tracing for Delta, according to a study in the American Journal of Infection Control (AJIC). Author Marvin Du, of the University of California, writes that contact tracing can play a “significant role” in lowering COVID-19 cases and delay the peak in cases. The onset of symptoms can be used to determine whether someone should be quarantined, but COVID-19 test results can help to quickly isolate asymptomatic and pre-symptomatic individuals.

“For the Delta variant, or other variants of much higher infectivity, contact tracing alone cannot significantly lower the number of daily new cases but is able to delay the peaks greatly, thus affording more time to explore and implement pharmaceutical interventions,” the study states.

Du categorizes contact tracing as the nonpharmaceutical intervention (NPI) that’s the least intrusive NPI when compared to lockdowns, masking, and social distancing. According to the website Our World in Data, 56.9% of the world’s population has gotten at least 1 dose of a vaccine, but only 7.6% of people in low-income countries have gotten 1 dose.

“When a vaccine is not available, NPIs can help ‘flatten the curve’ which helps gain valuable time to develop, manufacture, and distribute the vaccine,” the AJIC study states. “Even after a significant fraction, or even most, of the general population has been vaccinated, breakthrough infection by new variants of the virus among vaccinated people may still pose imminent threats, and NPIs can play an important role to combat the spread of infections.”

The study states that if test results for the original COVID-19 virus can be completed so that infected individuals can be isolated on the eighth day of infection then that would significantly reduce the number of new cases. If the infected individuals can be isolated within the sixth day of infection, it can nearly produce what the study calls a “crush the virus” effect—or stopping the spread. However, contact tracing alone would have to be used with other NPIs to achieve this result.

Also, the more people who’ve gotten vaccinated and/or a booster shot, the better.

“To deal with outbreaks caused by variants of SARS-CoV-2, preexisting immunity (gained either from vaccination or previous infection) can play a vitally important role to reduce the number of daily new cases,” the study states. “Therefore, vaccinating the general public not only helps combat the current outbreak but also makes future outbreaks easier to deal with.”

Contact tracing should be used no matter what the level of infectivity might be because, when done correctly, it usually leads to lower numbers of new cases.

“This may include defining ‘close contact’ more reasonably, making use of digital equipment such as smart phones to find individuals who may have close contact with those known to be infected, using test results to determine entry and exit to quarantine, providing support to the self-quarantined so they do not need to make trips to grocery stores and restaurants, maintaining daily contact with the self-quarantined, and providing support wherever and whenever necessary,” the study states.