A discussion and look into the near future of what may be possible for evaluating the risk of bringing a group of people together, for work, study or other activities, before the availability of a treatment and a vaccine for COVID – 19
The understanding of COVID-19 is a rapidly changing landscape as scientists and doctors around the world seek to find a cure and a vaccine. The amount of new information is enormous and what seems current knowledge today often become obsolete within hours or days, something which is unprecedented in medicine. And in spite of this intense research, there is, as yet, no cure and no vaccine.
This virus is a difficult to control. Symptoms of COVID-19 infection can cause illness that spans an entire spectrum from no symptoms, a runny nose and cough of a mild cold to fatal respiratory failure. In the serious cases, the virus can cause a severe inflammatory reaction in the lungs and impair its function, depriving vital organs of oxygen. The body begins to shut down from failure of multiple organs as the lungs lose its ability to exchange carbon dioxide and oxygen. As there is no cure for this infection, the only way to save these patients is by supporting respiration. Ventilators help these sick patients get through this crisis and give time for their lungs recover.
The transmission of this virus is by water droplets which is generated by coughing and sneezing. Certain medical procedures can also generate droplets such as intubation of a patient and is a major hazard for health care workers. Infection occurs when the virus enters the respiratory tract attaches to a receptor (ACE2) which is present in the lining of the airway. Protection of the eyes (tears drain into the nose), mouth and nose by shields and masks is essential to prevent infection. The virus cannot infect the skin which has no ACE2 receptors and wearing gloves is not useful for preventing COVID-19 infection. Hand washing and not touching ones face helps to keep the virus away from our eyes, nose and mouth.
As this virus makes its way around the world, it is becoming abundantly clear that we will have to live with the threat of COVID-19 in every sphere of our lives for some time to come. As we all think about returning to work and returning to school and to our social activities in the midst of an epidemic, how do we mitigate the risk of infection for our friends, family and co-workers? Checking temperature may be helpful but will not detect a significant proportion of infected individuals who carry the virus but are not febrile. Is there a better way? In our world of COVID-19, you either have immunity from a previous infection or you have no immunity. A test for COVID-19 protective antibodies, which is in development, combined with sensitive viral PCR swab test, might help us assess the risk. It all starts with defining your groups COVID-19 status.
The current PCR viral swab test is designed to detect the presence of the virus in the upper airway. The viral antibody test, on the other hand, is meant to test for immunity to the virus. For the purpose of the following discussion, we will assume that these tests have a high sensitivity and specificity that is better than what is currently available. In other words, these tests have the ability to correctly identify those with disease or immunity, as well as those who do not. Also, we have to assume that the antibody test will detect protective immunity. Doing these two tests at the same time, may be of value to organizers, employers and others to identify those in the group who are immune, non immune and those who carry the virus. The following describes the expected results depending on COVID status:
Covid – 19 Immune: PCR swab test NEG and protective antibody test POS
These individuals have been exposed to COVID-19 and are now immune. They are no longer contagious. Repeat antibody testing will be needed, however, to determine how long antibodies will last as the durability of the immunity is still unknown. Repeat testing will be needed to confirm immunity at set intervals, such as 6, 12, 18 months and so on. This group may need COVID-19 vaccination if immunity to the virus starts to wane over time.
Covid – 19 Non Immune: PCR swab test NEG and protective antibody test NEG
This is the vulnerable group and unfortunately, the majority of us in the world belongs to this category. Susceptible to the COVID-19, the only protection is prevention; hand washing, social distancing and isolation until we have a treatment or vaccine. As more information becomes available, it might be possible to employ risk factors and biomarkers to identify those who are susceptible to severe disease versus those who are not.
Looking into the fall and winter of 2020, it is especially important for those who have no immunity to COVID-19 to discuss vaccination for influenza and pneumonia with their own primary care provider. Having protection against influenza, which primarily infects the lungs, will not only prevent complications of the flu such as pneumonia, but also likely improve your chances of recovering from a COVID-19 infection.
COVID-19 immune “carrier”: PCR swab test POS and protective antibody test POS
There are reports that suggest the presence of carriers. This group is problematic as they have antibodies and at the same time still carry the virus. These individuals will likely show mild or no symptoms and are likely to spread the infection to others. The presence of antibodies may suggest a late stage infection that is resolving or possibly a carrier state that needs to be further studied. These individuals will have to self isolate and be monitored by public health. Follow up testing will help to confirm clearing of the virus from their system and development of protective anti COVID antibodies.
COVID-19 non- immune “carrier”: Viral RNA test POS and protective antibody test NEG
This group is similar to the immune carrier group and may reflect an early stage infection or a carrier state. And like the previous group, public health will be involved in the monitoring of these individuals. Careful clinical follow up and measurement of respiratory rate and blood oxygen saturation will be essential.
Doing these two tests will not only identify individuals who are contagious, it will also give a snapshot of the proportion of individuals in the group who are immune and those who are not immune. If the proportion of COVID immune individuals is high, for instance 80% immune and 20% non immune, the risk of a COVID-19 outbreak in the group will be quite low. The large proportion of individuals who are immune will make it difficult for the virus to spread. On the other hand, if only 20% are immune, the risk of an outbreak will be high. The degree of usefulness of these tests will vary between jurisdictions depending on the prevalence of the virus. In jurisdictions with very low or very high prevalence rates, testing may not be as useful as in those with intermediate prevalence.
By using these tests, we can have a better handle of the risks as we begin to think about gathering together again. Organizers and employers may be able to use these tests to assess the risk for their respective groups. Repeat PCR swab testing will be necessary to detect new carriers and repeat antibody testing will help to define the immune status of the group in the months to follow.
I want to emphasize the importance of following the guidance of our medical health officers as we look to re-open businesses and schools. The pressure to get the economy up and running again is great but doing it too soon may have severe consequences. Getting a second wave of infection will be disastrous. More patients will die and a second shut down may be necessary resulting in more anxiety and stress. Many businesses will not survive another four weeks of closure. We need to be patient and respectful of each other – we are all in this together.
Thank you to my wife Faith and my brother Dr. Timothy H. Lim for proofreading this article.
