- Johnson & Johnson is considering running a booster trial in SA, which will test the J&J and Pfizer vaccines as boosters.
- A booster dose with ImmunityBio's T-cell vaccine has already started in the country.
- The doses will be given to healthcare workers who partook in the Sisonke Covid vaccine study.
Talks are underway with Johnson & Johnson (J&J) and the Department of Health about running a Covid-19 vaccine booster trial in South Africa, Professor Glenda Gray, co-investigator of the Sisonke research study, told Bloomberg this week.
Close to 500 000 healthcare workers in SA have received the company’s vaccine as part of the Sisonke trial, which was launched in mid-February this year.
The trial would add to a booster study (that has already started) using ImmunityBio’s shot. It would include participants from the Sisonke study, according to Gray, who is also the president of the South African Medical Research Council.
In addition to the ImmunityBio shot, Gray said that they intend to investigate potential boosting with the J&J vaccine, as well as the mRNA jab by Pfizer-BioNTech. These multiple booster studies will allow for comparison about which vaccine would be best as a top-up to the J&J jab, she added.
Anticipating a fourth wave
Speaking to Health24, Gray said that this study is a proactive approach to stay ahead of the virus and a potential fourth wave.
“We know from the immunological studies that the J&J vaccine does hold up to about eight months, and we obviously don’t know beyond that because the data are still accumulating,” said Gray.
She added: “So the discussion has come up about when should one vaccinate people who received the [primary] dose, and the timing thereof, particularly the healthcare workers. Because we anticipate another wave and we have to make sure that the healthcare workers have got their immune responses before the wave.”
ImmunityBio, an immunotherapy company, announced in July 2021 that they had received authorisation from the South African Health Products Regulatory Authority (Sahpra) to conduct their Sisonke T-Cell Universal Boost trial.
The trial is currently in its first phase, with about 50 participants. It is expected to reach its third and final stage in October, with about 10 000 people receiving doses.
The company aims to determine whether the T-cell-based vaccine could prevent breakthrough infections from the highly transmissible Delta variant in healthcare workers who are already vaccinated.
The goal of the “second-generation ... T-Cell Covid-19 vaccine is to potentially provide increased protection and long-term immunity against the multiple variants and third wave infections currently affecting South Africa and other countries”, the company said.
Data from US promising
Phase 1 studies of the company's booster shot tested in the US have already demonstrated no serious side effects and “potent T-cell responses”, it added.
"[It induced] a 10-fold increase in T cell response – equivalent to T cell responses from patients previously infected with SARS-CoV-2 (the virus that causes Covid),” said Leonard Sender, Chief Operating Officer of ImmunityBio.
“We have also shown that the T cell responses are maintained against variants, which is critical to providing protection against this ever-changing virus,” he added.
Antibody versus T cell
ImmunityBio is particularly looking at a T cell vaccine. Although antibodies have been shown to block infection when present, T cells are vital for long-term immune memory, it said.
Antibodies defend a cell from the Covid virus, and while they normally decline over time, it is “memory” immune cells, including T cells, that work to prevent severe disease and death.
In the US, people vaccinated with the Pfizer or Moderna vaccine may be eligible to receive a third dose eight months after their second dose, due to waning immunity. With this plan, the CDC hopes to get ahead of waning immunity and avoid the chance of severe infection.
A booster shot of the J&J vaccine has not yet been recommended, since there is a lack of data.
Prolonging immune response
Gray said that it is likely that ImmunityBio’s T cell vaccine will “increase the magnitude of” and offer a more robust immune response to those who receive it.
Although local and international experts recently cautioned that rolling out booster doses at this point would be premature, as the vaccines remain effective at protecting against severe disease and death even several months after vaccination, Gray explained that they could help to prolong the immune response.
“We don’t want the immune response to wane and see how vaccine effectiveness declines. So the boosting is to prolong the immune response and make it more durable. It may protect against infection, and it also may prolong the durability of vaccine effectiveness against hospitalisation and death,” she said.
It’s important for scientists to get ahead “[before] it’s too late”, said Gray.
“If we are going to boost, we mustn’t wake up and find out we don’t know what a boost is, and we don’t know its timing. So this is all an anticipation of whether one needs to boost or not – [if we need it], we’ll have that information.”
Healthcare workers are also highly exposed to the virus, and giving them a booster shot in time for the potential fourth wave will ensure they are protected, said Gray.
Being fully vaccinated would put people in a better position during the imminent fourth wave, which is estimated to occur around November and December 2021, epidemiologist, Professor Salim Abdool Karim recently stressed during a media briefing, News24 reported. Karim is the former chairperson of the government's Ministerial Advisory Committee on Covid-19.
In terms of the expected severity of the fourth wave, Gray said: “We don’t have a crystal ball. We should always expect the worst.”