Top doctor’s letter on AstraZeneca and Delta variant ignites debate

A letter by a renowned doctor based at Nairobi Hospital has ignited debate on the effectiveness of the current nationwide Covid-19 vaccination programme after he claimed that the AstraZeneca vaccine has no effect on the Delta variant, which is the most dominant in the country.  

In the two-page letter, Dr David M Silverstein, a consultant cardiologist, disclosed that doctors had seen quite a few bad cases of Covid-19 in patients who are fully vaccinated with the AstraZeneca jab, so far the only vaccine available in Kenya. 

“We were previously told that being fully (double) vaccinated protected us against severe disease: That is not holding out to be true. 

“We are seeing severe disease in our population, especially in the elderly and those with co-morbidity, such as with diabetes, chronic kidney disease, connective tissue disease, those with cancers, with or without chemotherapy,” the letter reads in part.

The doctor further asks those travelling and who have access to other vaccines to take advantage of the doses. 

“If you are travelling and have access to an mRNA vaccine (Moderna or Pfizer), take advantage of getting vaccinated, even if you are doubly vaccinated with AstraZeneca. 

“Even if you can only get one of the vaccinations, do it,” he notes. 

There is a difference between an mRNA vaccine and a viral vector vaccine despite the fact that both contain instructions that teach our cells how to create "spike proteins" found on the surface of the virus that causes Covid-19.

Effectiveness of AstraZeneca

While mRNA is surrounded by tiny lipids (fatty molecules) which help it to enter your cells directly, in viral vector vaccines, spike protein DNA is placed inside a modified version of a different virus that doesn’t cause illness. 

This non-harmful virus delivers the DNA instructions to your cells – this virus is called the vector. 

But Dr Silverstein is not the first to raise the red flag on the effectiveness of AstraZeneca.

Earlier this year, two doses of the vaccine were found to have only a 10.4 per cent efficacy against mild-to-moderate infections caused by the B.1.351 South African variant, according to a peer reviewed clinical trial published in the New England Journal of Medicine.

Scientists explained that the South African variants share mutations with the other variants, leaving those vaccinated with the jab potentially exposed to multiple variants. 

This was why in February, the country suspended its rollout of the AstraZeneca vaccine, after clinical trials registered "disappointing" results against the variant, and asked Serum Institute of India for a refund for the unused 1.5 million doses the world’s biggest vaccine maker had delivered.

In an official response to the Nation on Wednesday, the Ministry of Health (MoH) said it had noted the concerns.

'Misleading opinion'

“While no vaccine is 100 per cent effective, they all -- including AstraZeneca -- protect against, and are effective against, severe Covid-19 disease.

“It should also be clear that Kenya has not adopted a vaccine mixing strategy, nor has it recommended a third dose, and these strategies are continuously on review as evidence evolves globally,” the response reads.

The ministry, however, agreed with Dr Silverstein on one thing. 

“In his letter, the doctor quite rightly advises that people should take either an antigen or PCR test. This is because the tests are good for confirming infection.”

Amref Health Africa CEO Gitahi Githinji, who is also an adviser of Kenya’s Covid-19 task force describes Dr Silverstein’s sentiments on the efficacy of AstraZeneca vaccine on the Delta variant as ‘his own personal misleading opinion’ which is not comprehensively backed by vaccine science.

“His sentiments are misleading. All vaccines are effective against severe Covid-19 disease but none of them is 100 per cent effective, according to all the studies that are available. 

“Which is why we are prioritising people with co-morbidities, all of us need to be worried because the Delta variant is more infectious that the other variants.

Lower effectiveness 

“We have breakthrough cases all over the world among people who have been inoculated with Pfizer, Moderna, as well as AstraZeneca, the point is, none of the vaccines is 100 per cent effective because data has shown all vaccines have lower effectiveness against the Delta variant,” said Dr Githinji.   

He is not wrong. 

While addressing a UK parliamentary meeting last week, Sir Andrew Pollard, a professor of paediatric infection and immunity at the University of Oxford, the developer of the AstraZeneca vaccine, said it was unlikely that herd immunity will be reached. 

"We know very clearly with coronavirus that this current variant, the Delta variant, will still infect people who have been vaccinated, and that does mean that anyone who's still unvaccinated, at some point, will meet the virus," he told MPs.

A recent study from the Chinese Academy of Medical Sciences has established that “viral loads in Delta infections are [approximately] 1,000 times higher” than those caused by previous Sars-CoV-2 variants.

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