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More evidence herd immunity won’t stop Covid-19

Health & Science - By Graham Kajilwa | August 30th 2020 at 12:00:00 GMT +0300

The first case of Covid-19 re-infection in the United States has added weight to the debate on the possibility of a second wave of the pandemic.

The US case comes just a week after another - the first one globally - was documented by scientists from the University of Hong Kong, China.

Unlike the Hong Kong case of a 33-year-old who was asymptomatic, the US patient, a 25-year-old, exhibited cough, diarrhoea, fever, and sore throat on May 31 when he was diagnosed positive again.

The patient, who is from Nevada, had been reported as recovered on April 27.

And unlike the Hong Kong patient who was re-infected with a different strain of the virus, the US patient appears to have been re-infected by the same strain.

Covid 19 Time Series


It is for this reason that scientists have ruled out a vaccine or herd immunity as the solution that will clear the pandemic.

Yesterday, Kenya’s Health ministry reported 164 new cases (and five deaths), raising the tally to 33,794 confirmed cases and 572 fatalities.

The ministry has warned there could be a second wave of infections locally if containment measures are relaxed.

The case documented in a study by the University of Hong Kong but yet to be published showed the virus which infected the patient a second time was weaker, hence no symptoms.

The study was accepted by the journal of Clinical Infectious Diseases on August 24.

Compared to the first incident where he tested positive and had symptoms synonymous with the disease – cough, sore throat, fever, and headache - for three days, he exhibited no symptoms the second time.

His first diagnosis was on March 26, while the second one was on August 15. Both specimens were analysed for genome sequencing (the process of determining the DNA of an organism).

“Genomic analysis showed that the first viral genome belongs to a different lineage from the second viral genome,” reads the study in part.

The patient in the second incident was returning to Hong Kong from Spain via the United Kingdom which suggests why there is a difference in the strain of the virus, which some scientists have argued could be weaker, hence the reason for not showing symptoms.

The confirmation of the reinfection, the study says, has key implications.

“First, it is unlikely that herd immunity can eliminate Sars-CoV-2 although it is possible that subsequent infections may be milder than the first infection as for this patient,” reads the study.

Due to this re-infection, the study says, Covid-19 will likely continue to circulate in the human population as in the case of other coronaviruses.

“Re-infection is common for seasonal coronaviruses and in some instances, re-infection occurs despite a static level of specific antibodies,” it adds.

Earlier, studies have shown that antibodies against the virus do last for about three months.

The study notes that from the findings, vaccine may not provide lifelong protection against Covid-19.

“Since immunity can be short-lasting after natural infection, vaccination should also be considered for those with one episode of infection,” it says.

Covid-19 Herd Immunity

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