Dr. Shira Doron of Tufts Medical Center and Dr. Davidson Hamer of Boston Medical Center answered questions about long COVID symptoms, holiday guidelines and new data that shows the Pfizer vaccine’s efficacy wanes over time.
COVID-positive individuals have reported experiencing a fever, cough, shortness of breath and many other symptoms associated with the virus.
But how long does it take for symptoms to appear once a person has been exposed? And when is COVID the most transmissible?
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According to the Centers for Disease Control and Prevention, the incubation period, the time from exposure to when one develops symptoms, ranges from two to 14 days after the initial exposure. Scientists caution, however, "the period of infectiousness" for COVID-19 is not yet known with certainty.
Furthermore, doctors warn that an individual can spread COVID-19 even before showing symptoms.
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A study co-led by a researcher from the Boston University School of Public Health found that those who've been infected are most contagious two days before, and three days after they develop symptoms.
Researchers also determined that infected individuals were more likely to be asymptomatic if they contracted the virus from a primary case.
While household members of primary cases had higher infection rates than other close contacts, close contacts were more likely to contract COVID-19 if they were exposed shortly before or after the individual developed noticeable symptoms.
According to the Massachusetts Institute of Technology, another study found that contagiousness both began and peaked before the first symptoms of illness — 2.3 days and 0.7 days respectively. Researchers concluded that about 44% of COVID-19 infections spread from person to person before symptom onset.
As a result, according to MIT's website, the CDC considers contract tracing, identifying close contacts, vital in protecting communities from further spread. A close contact is defined as someone who has been within 6 feet of a COVID-positive individual for a cumulative total of 15 minutes or more over a 24-hour period.
"Time is of the essence," the CDC's website stated. "If communities are unable to effectively isolate patients and ensure contacts can separate themselves from others, rapid community spread of COVID-19 is likely to increase to the point that strict mitigation strategies will again be needed to contain the virus."
