Sisonke trial: Researchers to start a mixed vaccine booster study

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  • The Sisonke trial will enrol 300 healthcare workers to test different vaccine booster options. 
  • The trial will test four booster vaccine formulations.
  • It will also look at how booster shots act in HIV positive people and those older than 55.

The Sisonke trial will soon start testing vaccine booster combinations on healthcare workers, according to a statement by the Wits Reproductive Health and HIV Institute (Wits RHI).

Wits RHI, together with CAPRISA eThekwini, and the Desmond Tutu Health Foundation in Masiphumelele, are currently recruiting approximately 300 healthcare workers to form part of a clinical trial that will compare the Johnson & Johnson and Pfizer Covid-19 vaccines as boosters.

“The purpose of this study is to evaluate immune responses to a prime-boost vaccination strategy and to see whether the different vaccine strategies, as well as the time between prime and boost doses influences immune responses,” the organisation said in a statement. 

The trial will collect data for six months.

Mixing vaccine boosters 

Healthcare workers who were part of the Sisonke trial were vaccinated with the J&J vaccine. This trial, called Booster After Sisonke Study (BaSiS), will test four different Covid-19 boosters in healthcare workers.

Healthcare workers will receive one of four options. The first option is a full dose of the J&J vaccine, the second a J&J half dose, the third a Pfizer full dose, and the fourth a Pfizer half dose. Healthcare workers will not be able to choose which booster they receive.

Lowering doses of vaccines are called fractional dosing and have been used in yellow fever and polio vaccination.

“Fractional dosing may reduce side effects following vaccination and may be particularly useful for boost doses since they result in a good immune response,” according to WitS RHI.

The BaSiS study co-chair, Professor Lee Fairlie, says that fractional dosing has public health benefits. 

“The benefits are around that the cut the doses of vaccines for boosters means that basically more people can actually be vaccinated for the same amount of vaccine vials that are available. It means that it reduces the [vaccine] costs and it also possibly means that it may reduce the effects that people from the vaccine, and this can be local side effects, pain and redness, and systemic side effects,” said Fairlie. 

Vaccines effectiveness for people living with HIV

Fairlie says that the study will have a third of its participants who are HIV positive to test how well booster shots work in HIV positive people.

“We always need to consider that we know there are around eight million South Africans living with HIV, and we really need to know whether our current boost options are actually optimal for people living with HIV,” she said.

The trial will include participants who are 55 years and older (10%) to gather data on immune responses in older people where progressively weakened immune responses are a concern.

*For more Covid-19 research, science and news, click here. You can also sign up for our Daily Dose newsletter here.

READ | Covid-19: Age, underlying conditions may put some vaccinated adults at higher risk of severe illness

READ | Menstrual cycle changes a potential side effect of Covid-19 vaccination, study finds

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