Epidemiologist AMA FAQ

This FAQ comes issue 05 of Recap where members of the MICA community were able to ask questions to two epidemiologists. The questions featured in the issue, as well as answers from Dr. Anthony Harris and Dr. Jonathan Baghdadi, can be found below. 

Q: What is the efficacy of a PCR nasal swab test? What is the probability of a false negative or false positive? If the tests are to be self-administered, how do medical professionals ensure tests are performed correctly?

A: The PCR test is considered the gold standard for diagnosis of COVID-19, and it is the test that we have the most experience with. However, it is not a perfect test.  In particular, the performance of the PCR test varies depending whether someone with COVID-19 has symptoms and, if so, how long ago their symptoms began. If testing is performed around the time symptoms develop or within 5 days of onset of symptoms, the PCR test will detect >90 out of 100 individuals with COVID-19. Performance of the PCR test is not as well understood in asymptomatic individuals, so it is hard to estimate the false negative rate, but based on comparisons between PCR and other types of tests, it should be the most sensitive test that is able to detect the most cases of COVID-19.

Unfortunately, false positives do occur, but they are relatively rare. In particular, we know that individuals who previously recovered from COVID-19 may continue to test positive by PCR, even though they no longer have active infection and they are no longer infectious to the people around them.

It is also important to remember that any kind of test may not detect SARS-CoV-2 while it is “incubating.” The incubation period is the time that passes between when an individual is exposed to the virus and when they develop infection. The typical incubation period for SARS-CoV-2 is 5 days. Thus, a negative test today does not guarantee a negative test tomorrow. This is why testing is only one component of an effective campus policy.

The nasal swab specimen is easy to collect because it does not need to go far back into the nose. When researchers have compared the performance of PCR testing using self-collected specimens vs. specimens collected by trained professionals, the self-collected specimens are just as good. Many colleges have implemented testing protocols that require students and/or staff to self-collect specimens. These instructions may be helpful: https://www.cdc.gov/coronavirus/2019-ncov/downloads/community/COVID-19-anterior-self-swab-testing-center.pdf

Q: As MICA looks ahead to a partial reopening this Spring semester, what are the most important public health protocols you would advise the College and our community to be emphasizing?

A: At this point, important public health protocols are well-known.

Whenever possible, masks should be worn when in the presence of others. Eye protection, such as goggles or a face shield, can add an additional layer of protection. When working alone in a private space, a mask is not needed.

When sharing a space with someone else, as much physical distance as possible should be maintained.

When using shared equipment, perform hand hygiene frequently and avoid touching your face.

If you have symptoms of a cold, such as fever, cough, sore throat, headache or muscle aches, notify your supervisor and do not come to campus. Loss of taste or smell is also a symptom that people with COVID-19 sometimes report.

On top of these basic steps, MICA has taken steps to enhance the environmental disinfection of campus spaces.

The most difficult thing to manage in terms of protecting your own health and the health of those around you will be eating and drinking. Eating and drinking are high risk activities because people like to do them together, and they cannot be done while wearing a mask. In our experience, the highest risk exposures almost always occur around a meal. If you would like to eat together with colleagues, try to find a big room and separate by as much space as possible. Indoor dining at bars and restaurants seems very risky, even if it is technically allowed by city regulations.

Additionally, though they do not get as much attention, gyms are high risk. Forceful breathing can expel viral particles farther distances than normal breathing, and people may not feel comfortable exercising in a mask. Even a mask that is on at the begin of a workout may slide out of place or become soiled, which can reduce its protective effect.

The protocols that MICA is developing will likely change over time, since the science behind COVID-19 is still evolving. We will work with them to stay up to date.

Q: Thinking about the metrics that help inform MICA's Operational Modes, are they guidelines or hard and fast "triggers" where a change in one automatically alters MICA's Operational Mode?

A: MICA will be reviewing a number of metrics to monitor the level of risk to students, teachers, and staff. These metrics incorporate city data, state data, data from MICA on-campus testing, and data related to testing and isolation capacity. None of these metrics can be used in isolation or without considering the broader context of the pandemic. The metrics will be reviewed on a weekly basis by a group of key stakeholders and University of Maryland epidemiologists. These metrics provide a guideline rather than an automatic trigger. We have set thresholds for each metric to help identify when risk may be considered elevated, but the decision to change or keep an operational mode will be up to campus leadership.

Baltimore City Dashboard

Maryland State Dashboard

Q: Staying with the Operational Modes, and understanding that MICA is planning for a Spring opening in Operational Mode 3, what would you want to see to advise MICA to adjust down to Operational Mode 2 or up to Operational Mode 4 for opening?

A: This is a tough question, because we anticipate that the number of cases of COVID-19 will likely increase after Christmas. If City or Statewide numbers stay very high and do not appear to be coming down in early January, we may advise campus leadership to move to reopen at Operational Mode 2. Similarly, if early on-campus testing reveals a high positivity rate among students or staff, we would advise shutting down some campus services. Our top priority is to protect staff, teachers, and students.

For the sake of caution, we would not recommend reopening at an Operational Mode above 3. In order to move to Operational Mode 4, we would hope to see very low positivity rates among students and staff during on-campus testing, reliable and consistent testing providing timely results, and high fidelity to recommendations for mask use. Though the decision is ultimately up to campus leadership, we would not recommend moving to Operational Mode 4 until one of the scheduled breaks in the semester.

Q: What is presently known about the efficacy of testing in general? What factors went into your recommendation to MICA that weekly, asymptomatic testing for individuals regularly accessing campus was an appropriate approach?

A: Much of what is known about different strategies for testing comes from epidemiologic models, which are based on the real world but are not the real world. We recommended weekly asymptomatic testing based on modeling that shows it can expedite early detection of COVID-19 infections and reduce the number of high-risk exposures to COVID-19. Weekly asymptomatic testing has become standard practices at many colleges that have successfully reopened.

We did not recommend more frequent testing based on what we think will be feasible and safe in the long-term. Our goal is to maximize case detection while preserving capacity for testing, avoiding supply shortages, and preventing a backlog. The goal is not only that people get tested, but also that once testing is performed the results are available within a day or two.

If implementation of weekly testing is successful and does not strain available testing resources, we may recommend increasing the testing frequency.

Q: You have recently advised MICA that asking for a "pre-test" — a test taken several days to a week before traveling to campus — was not necessary. Can you walk us through that recommendation?

A: The basic goal is that everyone coming back to campus will have a recent negative test. In our own experience, access to testing can be variable and the turnaround of results can be slow. In some cases, tests sent to commercial laboratories may take a week or longer to provide a result. In other cases, individuals who tried to access PCR testing were instead tested on a rapid platform, producing variable results. We were concerned that asking every individual to sort out their own plan for testing could lead to chaos.

Instead, we have requested that all students, staff, and teachers returning to campus access testing through the MICA testing program. This way, testing can be accessed and resulted uniformly without confusion or delays with a testing platform that we trust. If possible, individuals who are local can arrange to come 2 or 3 days early to have their test performed, so that the results will be available by the time they arrive on campus. Teachers who cannot come early to be tested should avoid in-person instruction until after their first test has resulted negative.

Q: What information can you share about the vaccines currently being developed and how they might become available to the general population?

A: There are as many as three vaccines that may be approved via the emergency use authorization pathway by the end of this month. The manufacturers are Pfizer/BioNTech, Moderna, and Astrazeneca. The Pfizer and Moderna vaccines will be reviewed by the FDA on December 10 and 17, respectively. The date of review for the AstraZeneca vaccine has not been set yet. Each vaccine requires two shots, and each has been demonstrated in phase III clinical trials to protect vaccinated individuals against infection in the weeks after they receive the second shot. Data on longer term immunity has yet to be released.

The CDC has released guidance regarding decisions about who should receive vaccination first. Healthcare workers, essential workers, and individuals at risk for severe infection are considered candidates for early vaccination. The state of Maryland has not yet determined how to define essential workers, but teachers will likely fall into this category. Vaccination will be strictly voluntary (but we will definitely get it as soon as it is made available to me). Timing of vaccine distribution will depend on the supply that is provided to the state of Maryland and demand among potential candidates for early vaccination.