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September 23, 2020

Are There Covid-19 Reinfections?

Within the last weeks Covid-19 reinfections were reported in 4 patients, separated in time from their first episode.  Sometimes patients continue to have a positive molecular virus test after their Covid-19 infection, but the PCR test is able to measure remaining dead virus after recovery. RNA viruses mutate slowly, usually in unimportant portions of the virus.  The ability to sequence the RNA allows scientists to detect mutations - and that is how they determined that NYC was infected with a European strain of SARS-CoV-2, not the Wuhan strain.  The European strain was infecting communities in NYC long before there was any control of the planes arriving from Europe or even China. 

I was surprised that in the 4 patients with recurrent disease (one each from China, Belgium, Netherlands, and Nevada), scientists were able to compare the SARS-CoV-2 virus that was isolated from both their first and second positive SARS-CoV-2 virus samples.  There were different mutations present when the rwo samples were compared, thus demonstrating that these were 2 separate infections in each patient.  It is not clear how many cases of reinfection will be reported, virus samples from each episode must be available for testing.  These cases were each reported online, not in published scientific papers that I could find. 


September 19, 2020

What is a Covid-19 "Long Hauler?"

These are patients who have continuing symptoms for 4 or more weeks after Covid-19.  Symptoms can last more than 4 weeks after mild cases of Covid-19, and more than 8 weeks after hospitalized cases.  Unfortunately symptoms can last for months.  Many of the current long haul patients couldn't get a virus test when they first became ill because of the restrictions on testing.  But many of them now have positive antibody tests documenting the virus. 

Symptoms are very variable among patients, and in general they haven't returned to their pre-infection status.  There are respiratory symptoms, cardiac symptoms, decreased taste/smell, myalgias, headache, sleep problems, clotting disturbances, skin rashes, foggy brain, and fatigue mirroring chronic fatigue syndrome.  Although there are theories about the cause including continued infection or immune response to the virus and/or virus debris, the cause is unknown.  The incidence is greater than has been seen with other viral infections, and specialized centers are being developed to assess these patients and test therapies.  Long hauler patients are advised to locate one of these centers.


September 16, 2020

How Will We Drink Our Wine?

The Risks of Developing a Covid-19 Infection: From Morbidity and Mortality Weekly Review (CDC)

Just as New York City set a date to open indoor dining, the CDC released results from a study they did during the month of July on Covid-19 risks associated with various settings and exposures.  They found that restaurant eating and bar/coffee shop attendance had almost 2-3 times the risk for developing Covid-19, in comparison to many other activities.  The methods of the study were classic - a cohort of Covid+ patients from 11 trial sites were compared to a cohort of Covid-19 negative patients.  Everyone had to answer a battery of questions about their activities in the two weeks before their symptoms and virus tests.  Questions included mask wearing, and common activities: shopping, gym, salon, church/religious events, office work, and public transportation.  Only eating in restaurants, bars/coffee shops were statistically significantly associated with Covid-19 positive tests.  The lack of social distancing and mask use, while talking and eating, all contribute to the risk - outside or inside according to the data.



September 12, 2020

Vaccine Update - Halting One Trial

There are 3 vaccines that are in Phase 3 Trials in the US - each with a goal of enrolling 30,000 people - half to receive the vaccine and half to receive placebo.  They are vaccines from Moderna, Pfizer/BioNTech, and Oxford/ AstraZeneca.  No one will know what each person received until the end of the trial.  However there are independent Data and Safety Board Monitors and they can "unblind" the trial if there are problems. 

This week a person in the UK AstraZeneca trial developed a neurological problem and all of their trial sites were halted until the person can be fully evaluated to determine the cause.  They currently have trials in the UK, Brazil, South Africa and the US, although the trial in the US just started.  To date thousands of volunteers have received this vaccine in the UK.  In July they also briefly halted the trials and the volunteer was diagnosed with a previously unknown disease.  The safety considerations during vaccine development are paramount.  Yes, scientists want the vaccine to be efficacious, but safe.  Read more below.


Moderna and Pfizer have each enrolled about 20,000 healthy volunteers to date - each person gets 2 doses (21 days apart -Pfizer- or 28 days apart- Moderna).  Subjects are followed and tested regularly for safety and efficacy and the followup continues even after the vaccine is approved. 

Clinical Trial Approval Process that all vaccines, drugs, and medical devices must conduct to apply for FDA approval. 

Phase 1 trials are small (ex 50 volunteers) - to test different doses and assess safety.

Phase 2 trials have hundreds of volunteers and safety is still being assessed.  Vaccine effectiveness and antibody production is being measured in randomly assigned vaccine and placebo groups.

Phase 3 trials have thousands of healthy volunteers, randomly assigned to vaccine or placebo groups. Safety is still assessed, while effectiveness is measured.



September 9, 2020

College Students Return to Campus and Covid-19

There are now thousands of new Covid-19 cases on college campuses as students and staff return for the Fall semester (estimate 51,000 yesterday). Many schools have been forced to close down and send students back home.  Students were tested on arrival and additional means to control the virus are being tried.

The University of Arizona tried a technique that was used previously in polio epidemics in the 1930 to identify community outbreaks.  A small sample of pooled waste water from sewage is one of the first ways to detect the virus in a community, as the virus is shed very early from the GI tract.  Students were all negative when they arrived on campus, but during the waste water testing process one dorm was positive.  All of the 311 students were tested by molecular testing and 2 of the students were positive and could be isolated.  A recent update showed that a total of 46 students were now positive, among 10,000 antigen tests  Hopefully this is a manageable number for tracking and isolation and the campus can stay open. 


Other schools have set up twice weekly wastewater surveys, including Syracuse, Univ. of California San Diego, and Rensselaer Polytechnic Institute according to the press report  and can identify and quarantine positive students - keeping everyone on campus.  This is a good strategy for detecting small outbreaks and containing them on campus.