1/ Hong Kong reports the first confirmed case of SARS-CoV-2 reinfection today.
Although it is only a single case, it supports the theory that T-cell immunity (as opposed to antibodies) may be more important in regards to disease course and transmission.
Here's why.
Although it is only a single case, it supports the theory that T-cell immunity (as opposed to antibodies) may be more important in regards to disease course and transmission.
Here's why.
2/ Case summary:
A 33-year-old confirmed case of COVID-19 from March 2020 (positive PCR test along with fever, headache, cough and sore throat) tests positive in routine screening at the Hong Kong airport in August.
This reinfection occurred 142 days after his first infection.
A 33-year-old confirmed case of COVID-19 from March 2020 (positive PCR test along with fever, headache, cough and sore throat) tests positive in routine screening at the Hong Kong airport in August.
This reinfection occurred 142 days after his first infection.
3/ The patient was completely asymptomatic during the course of the second infection.
He did not have a fever, cough, headache or sore throat during the entire course of the reinfection.
Based on genome sequencing though, it is likely that it is a true second infection.
He did not have a fever, cough, headache or sore throat during the entire course of the reinfection.
Based on genome sequencing though, it is likely that it is a true second infection.
4/ Did antibodies protect him from symptoms?
Probably not...lab tests did not detect any long-term IgG antibodies during the first few days after reinfection.
It's more likely the patient had T-cells that recognized the virus early—eliminating it before developing symptoms.
Probably not...lab tests did not detect any long-term IgG antibodies during the first few days after reinfection.
It's more likely the patient had T-cells that recognized the virus early—eliminating it before developing symptoms.
5/ What does this mean for herd immunity?
Asymptomatic patients are likely to be less infectious than symptomatic patients.
This is also true for the flu and common cold coronaviruses.
According to the NHS, seasonal colds and the flu are most infectious after symptoms begin.
Asymptomatic patients are likely to be less infectious than symptomatic patients.
This is also true for the flu and common cold coronaviruses.
According to the NHS, seasonal colds and the flu are most infectious after symptoms begin.
6/ Multiple T-cell studies have shown that about 50% of participants BEFORE the COVID-19 pandemic already possessed SARS-CoV-2 specific T-cells that may be protective against COVID-19.
This could be due to prior exposure to common cold coronaviruses.
This could be due to prior exposure to common cold coronaviruses.
7/ In regions hit hardest by COVID-19, cases/deaths consistently peak at ~20% infected based on serology tests (e.g. Lombardy, Madrid, London, NYC, Stockholm).
Then deaths decline.
Again, Sweden without lockdowns or masks has curves consistent w/ natural herd immunity.
Then deaths decline.
Again, Sweden without lockdowns or masks has curves consistent w/ natural herd immunity.
8/ There is a good chance that ~70% of the population in these cities/regions now possess T-cells protective against COVID-19.
Those w/o prior T-cell immunity from common cold coronaviruses likely facilitated spread of the virus and suffered the worst outcomes in the first wave.
Those w/o prior T-cell immunity from common cold coronaviruses likely facilitated spread of the virus and suffered the worst outcomes in the first wave.
9/ Many regions of the world still under lockdown and with mask mandates in place may actually possess the same degree of herd immunity as Sweden.
This could mean unnecessary hardship on children, families, employment, small businesses and the economy overall.
This could mean unnecessary hardship on children, families, employment, small businesses and the economy overall.
10/ In conclusion, there's a case report of SARS-CoV-2 reinfection whereby T-cell immunity may have been protective.
This is just a single case.
However, it lends support that T-cells may be more important than antibodies in COVID-19 disease course and natural herd immunity.
This is just a single case.
However, it lends support that T-cells may be more important than antibodies in COVID-19 disease course and natural herd immunity.
