Facing flagging demand from the public and a stockpile of millions of coronavirus vaccines with midyear expiry dates, the government has slashed the interval between jabs and announced that adults can have different shots when they go for their boosters.
SA has 21-million vaccine doses of Johnson & Johnson’s (J&J) and Pfizer/BioNTech vaccines on hand, with 7-million Pfizer jabs expiring by midyear, said health deputy director-general Nicholas Crisp.
Less than half the country’s adults have been inoculated, and the seven-day moving average of daily vaccinations stands at just 64,200, a far cry from the August peak of about 241,230, Our World In Data shows.
This situation, combined with the ability of Pfizer’s jab to be used "off label’’ with other coronavirus vaccines, has prompted the strategy change, Crisp said.
SA has until now offered people a primary course of either a single J&J shot or two jabs of Pfizer’s vaccine six weeks apart, each followed by a booster of the same shot.
From Wednesday the interval between the first two Pfizer jabs has been halved to three weeks, and the time to a booster has been cut to three months instead of six. The booster can be either a third Pfizer shot or a J&J jab. From Monday, adults who received a primary J&J shot became eligible for a booster of either vaccine two months after their first jab.
The department of health said people should ideally stick to the same vaccine, but they could opt for a mix-and-match approach if they want to, if that is all that is available at their chosen vaccination site or if they have experienced severe side-effects from their first shots.
The government has stopped short of recommending a mix-and-match strategy, because while it is safe, the evidence is insufficient that it offers superior protection to boosting with the same vaccine, Crisp said.
The interval between Pfizer shots has been cut because people are more likely to get their next shot if the wait between jabs is reduced, he said.
Wits University vaccinologist Shabir Madhi said the change is long overdue, as a mix-and-match strategy is likely to offer better protection against infection and severe illness than repeated doses of the same vaccine. Two vaccines on offer in SA are based on different technologies, and each elicits a different response from the body’s immune system, he said.
The J&J shot is an adenoviral vector vaccine, which prompts a stronger T-cell response, while the Pfizer jab is an mRNA vaccine, which triggers a stronger antibody response, he said.
Madhi questioned the timing of the announcement, saying he has been calling for a mix-and-match strategy for months.
"In the past the health department has argued — and it did not make any sense — that it was not approved by Sahpra," he said, referring to the SA Health Products Regulatory Authority.
"All of a sudden that does not seem to be a factor. I suspect the only thing causing them to come up with a sudden rush of recommendations is they have vaccines expiring some time soon."
By Sunday, 42.3% of adults in SA were fully vaccinated, government statistics show.
SA Medical Association Gauteng chair Mark Human welcomed the decision to allow mix-and-match vaccination.
"For several months top virologists have been calling for heterologous boosters, and it is little secret that many doctors have done it. Complementary immunity from different types of vaccine will probably give you a broader spectrum of immunity," he said.
Medical Research Council president Glenda Gray said studies investigating mixing and matching vaccines have shown the strategy increases the breadth of the body’s immune response. But real-world data on how effective this approach is at preventing infection or severe illness is still emerging. "A lot of people say you can extrapolate from the immune response that there will be improved efficacy, but only large-scale studies will show this," she said.
The department will update the electronic vaccine data system to enable people who received their primary course outside SA to register on the system and receive booster shots in SA. It also said it no longer requires a two-week interval between coronavirus shots and vaccines for other diseases, such as influenza.
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