Differences over vaccine treatment for transplant recipients

RAY HARTLE

There is no agreement among South Africa’s heart transplant programmes that Covid-19 vaccination will be recommended for donor heart recipients.

While a vaccine is keenly anticipated as the best means for immunosuppressed transplant recipients to counter Covid-19, not all transplant recipients in SA will necessarily benefit from the vaccine treatment the country procures.

Groote Schuur Hospital (GSH) respiratory physician Dr Greg Calligaro, a member of the state-funded hospital’s transplant programme, quoted comments by Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, to the effect that, on balance, immunosuppressed individuals should be vaccinated against Covid-19.

Although SA’s department of health will procure 1.5m doses of AstraZeneca vaccine from the Serum Institute of India (SII), renamed Covishield in that country, it is not entirely clear which vaccines will ultimately be available for most South Africans.

As a result, the transplant programme at Durban’s Busamed Gateway private hospital is not yet recommending vaccination for organ recipients.

Durban transplant surgeon Dr Robert Kleinloog said that until the government confirms which vaccines will be authorised for use in the country, “we rather say [to patients] ‘stay away’ [from vaccines] until we know which one is coming to SA”.

His approach is in keeping with directives in his programme that organ recipients should not receive the annual flu vaccine, whereas the other programmes routinely advise patients to get the flu shot.

“If it’s a live vaccine, we don’t advise they take it; if it’s a dead vaccine, we say they can take it,” he said.

Typically, in order to trigger an appropriate immunisation response in the human body, vaccine manufacturers use either a live infectious agent but one which has been weakened, referred to as a live attenuated vaccine, or a non-live, inactivated part of the infectious agent.

Organ transplant recipients take a daily regime of immunosuppressant drugs to lower their immune system’s natural tendency to treat the transplanted organ as a foreign object which must be rejected.

Any vaccine which includes live virus cells,-may break through the transplant recipient’s suppressed immune system and cause the recipient to contract Covid-19.

These implications are spelt out by Dr Melinda Suchard, head of the centre for vaccines and immunology at SA’s National Institute for Communicable Diseases, in an October 2020 note.

“For people with weak immune systems, live vaccines should be avoided but non-live (inactivated) vaccines can be given. In fact, the non-live vaccines become even more important to protect the person from possible future infections.”

SA does not have a single, uniform and legislated protocol for the various organ transplant programmes.

“There are always institutionally defined differences,” said Dr Susan Vosloo of the private Netcare Christiaan Barnard Memorial Hospital (CBMH) in Cape Town, adding that there should be a single protocol on Covid-19 vaccination for the country.

CBMH’s Dr Willie Koen said emphatically “an effective vaccine is the only option” for protecting heart recipients from the threat posed by the coronavirus.

Quoting Fauci, Calligaro said: “The advice we should be giving people [regarding] Covid vaccination is very clear. Patients on immunosuppression should be given any of the two Covid vaccines — the mRNA-based vaccine or the ones using the adenoviral vectors.

“Both of them are safe. The potential for harm seems low and our international body has come out very strongly advocating the use of [these vaccines].”

“We don’t know anything of the efficacy in transplant patients. We can assume that they won’t be as effective as in patients with intact immune systems for all the obvious reasons. There’s never been a vaccine shown to stimulate the immune system and cause rejection [of a donor organ].”

But Vosloo, who said she was “not an anti-vaccine individual — I take the flu vaccine”, said there were “a lot of questions over the vaccines which are not completely answered”, given the rush to have a treatment.

“Obviously, a live vaccine is more of a problem than the alternate,” said cardiothoracic surgeon at Netcare Milpark Dr Martin Sussman.

The Oxford AstraZeneca vaccine is a “recombinant” vector, or carrier vaccine, which uses an “adenovirus” — named after the human adenoids — that typically causes colds in chimpanzees, the NY Times reported.

“They genetically altered the virus so that it carried a gene for a coronavirus protein, which would theoretically train a person’s immune system to recognise the real coronavirus”, explained the newspaper.

According to the US government’s Vaccine.gov website, recombinants “give a very strong immune response” and “can also be used on almost everyone who needs them, including people with weakened immune systems and long-term health problems”, although booster shots may be required. This is similar to the requirement for vaccine shots developed from an inactivated agent which may be less effective over time.

Neither of the major vaccines produced in the US, the Pfizer/BioNTech and Moderna vaccines, use live agents. Instead, both use “messenger ribonucleic acid” (mRNA) technology to send a message to cells which trigger an immune response. But mRNA molecules are fragile and require storage at ultra-low temperatures.

Until the latest development to procure the vaccine directly from SII, SA initially was touted to have placed an order through the international Covax collaboration, an initiative of the World Health Organisation which has placed orders with Oxford/AstraZeneca and Moderna.