Re: Covid-19: Past infection provides 83% protection for five months but may not stop transmission, study finds
Dear Editor
I am sceptical of the findings of this study which claims that having had covid-19 previously provides 83% immunity protection for 5 months.
Firstly the study was carried out among healthcare workers not the general public who may have certain underlying conditions such as Diabetes, COPD, cardiac issues. So the findings may not be directly representative of the population at large.
Secondly, there are now 33 well documented cases of people around the world having repeated covid-19 reinfection. These cases are listed on the Cov-19 reinfection tracker website with literature citations which is constantly being updated. There well be many more cases of cov-19 reinfection being under reported. The PCR test has a serious short coming. It cannot definitively prove someone is infectious with live Sars-cov-2 virus.. This can only be established by a differential viral culture. It is possible for someone to have a positive PCR test result but be free of live virus as the test detects residual RNA fragments from a previous infections weeks after recovery. A negative PCR test result does not necessarily mean someone is not infectious, they may be incubating the virus again this would need a viral culture taken at the same time to confirm the person is not infectious. Were the PCR test results reported in this study confirmed by taking simultaneous viral cultures to determine infectious status?
Thirdly, the mean interval between covid-19 reinfection among the recorded 33 cases is 87 days, which is just under 3 months, much less than the findings of this study, so having a previous covid-19 infection may only give barely 3 months immunity. This suggests that the Chief Medical Officer's advice on extending the interval between Pfizer vaccinations from 3 to 12 weeks to be unwise as someone could easily acquire an infection between vaccinations.
My concern over vaccines is the manufacturers cannot quantify how long immunity protection might last, nor can they confirm whether they prevent viral transmission, nor can they adequately predict long term unintended adverse effects. In a sense the vaccine roll out in the population is substituting for a massive cohort challenge study.
Rapid Response:
Re: Covid-19: Past infection provides 83% protection for five months but may not stop transmission, study finds
Dear Editor
I am sceptical of the findings of this study which claims that having had covid-19 previously provides 83% immunity protection for 5 months.
Firstly the study was carried out among healthcare workers not the general public who may have certain underlying conditions such as Diabetes, COPD, cardiac issues. So the findings may not be directly representative of the population at large.
Secondly, there are now 33 well documented cases of people around the world having repeated covid-19 reinfection. These cases are listed on the Cov-19 reinfection tracker website with literature citations which is constantly being updated. There well be many more cases of cov-19 reinfection being under reported. The PCR test has a serious short coming. It cannot definitively prove someone is infectious with live Sars-cov-2 virus.. This can only be established by a differential viral culture. It is possible for someone to have a positive PCR test result but be free of live virus as the test detects residual RNA fragments from a previous infections weeks after recovery. A negative PCR test result does not necessarily mean someone is not infectious, they may be incubating the virus again this would need a viral culture taken at the same time to confirm the person is not infectious. Were the PCR test results reported in this study confirmed by taking simultaneous viral cultures to determine infectious status?
Thirdly, the mean interval between covid-19 reinfection among the recorded 33 cases is 87 days, which is just under 3 months, much less than the findings of this study, so having a previous covid-19 infection may only give barely 3 months immunity. This suggests that the Chief Medical Officer's advice on extending the interval between Pfizer vaccinations from 3 to 12 weeks to be unwise as someone could easily acquire an infection between vaccinations.
My concern over vaccines is the manufacturers cannot quantify how long immunity protection might last, nor can they confirm whether they prevent viral transmission, nor can they adequately predict long term unintended adverse effects. In a sense the vaccine roll out in the population is substituting for a massive cohort challenge study.
References:
Covid-19 Reinfection Tracker. BNO News
Competing interests: No competing interests