The SA Department of Health is not planning to buy the new Covid-19 bivalent booster vaccines, specifically tailored to target Omicron variants, anytime soon, writes Adele Baleta for Spotlight. Instead, people will continue to be offered the standard booster Pfizer-BioNtech and Johnson and Johnson (J&J) vaccine doses.
Vaccine experts have advised that anyone over 60, especially those with underlying conditions who have not had their fourth dose, should do so as soon as possible.
Health Department spokesperson Foster Mohale said the Vaccine Ministerial Advisory Committee (VMAC) has decided the bivalent or “updated” vaccines, approved for use in the United States by the Food and Drug Administration (FDA), are not a priority because they are not registered for use here and there is no “compelling evidence of their superiority over standard vaccines”.
“We have enough stock of perfectly good vaccine,” Mohale added.
Currently, the department has a massive stockpile of 29.7m Covid-19 shots, having ordered enough doses for the entire adult population. However, dwindling cases and hospital admissions have seen demand sharply drop.
The department said that by 6 February, 22.5m people in the country had received at least one dose. On 30 January, another round of booster doses of either the Pfizer or J&J vaccine was made available for the over-50s to get a fifth dose and those aged 18 to 49 a fourth dose.
Previously, Health Minister Dr Joe Phaahla said the government had been inundated with requests from fully vaccinated people, especially those most at risk, for booster doses to protect them against current and evolving Covid variants. By 6 February, a total of 19 102 booster doses have been administered in the seven days prior. The total number of boosters since the start of the booster campaign by then stood at 4.2m.
Several people have contacted Spotlight to ask when SA will have access to the bivalent vaccines. Some South Africans have taken advantage of the updated vaccine while visiting the US, believing it to be a better vaccine. The US Centres for Disease Control & Prevention (CDC) recommends that all age groups, with a few exceptions, get a single bivalent boost after having received the primary series (initial doses) of the vaccine.
Private sector procurement
Mohale said private companies and healthcare providers wanting to buy Covid-19 vaccines, including bivalent vaccines, must be registered with the South African Health Products Regulatory Authority (Sahpra). “Unfortunately, the doses will not be a part of the national programme and will not be recorded on the Electronic Vaccination Data System.”
Sahpra spokesperson Yuven Gounden said no private manufacturer or company had registered a bivalent booster vaccine with the regulatory body.
Monovalent vs bivalent
In 2020, all Covid vaccines were designed to prevent disease caused by the original Wuhan-1 strain of SARS-CoV-2, (the ancestral strain). These are called monovalent (one virus strain) vaccines.
Since then, the virus has rapidly evolved, replacing the original virus with numerous variants, able to evade the body’s immune system and lower the efficacy of these vaccines. Omicron, with its subvariants, is the most dominant and transmissible strain, resulting in breakthrough infections and reinfections.
The benefits of the mRNA technology used in the vaccines made by Pfizer/BioNTech and Moderna is that vaccine formulations can be tweaked to match a quickly changing virus. For better protection against the Omicron variant, Moderna and Pfizer-BioNtech updated their jabs to accommodate two virus strains (bivalent).
Half of the vaccine targets the original strain, the other half targets the BA.4 and BA.5 Omicron subvariant lineages, including the XBB1.5, which has a mutation believed to help the virus bind to cells, making it more transmissible.
Are bivalent vaccines more efficacious?
Dean of the Faculty of Health Sciences and Professor of Vaccinology at the University of the Witwatersrand Shabir Madhi agrees with the VMAC that the scientific data on bivalent boosters are not compelling enough. This is especially so for protection against severe disease and death, which he says is more durable – there is less waning immunity – than in trying to protect against mild disease or against infection.
The World Health Organisation’s position is the same, with its Strategic Advisory Group of Experts on Immunisation saying it’s important to get boosted, but that can be with either the monovalent or bivalent vaccine, Mahdi said.
Observational studies comparing monovalent to bivalent boosters show that while the latter has some additional (probably transient) benefit in preventing infection against Omicron variants, almost all studies show no additional benefit of the bivalent compared with monovalent boosters against severe disease.
Madhi said protection against severe disease is due to T-cell immunity, which has been relatively spared despite the mutations occurring with Omicron. “Protection against severe disease will be similar because the bivalent is not introducing a different repertoire of T-cell responses against Omicron.”
Protection against mild-to-moderate disease
Madhi said while data showed the bivalent booster induced more neutralising antibodies against the Omicron variant, including XBB1.5, immunity wanes. “So although the bivalent vaccine offers some benefit in protecting against mild-to-moderate Covid, that benefit is somewhat transient, probably lasting 16 to 20 weeks.
“You are back to square one, probably in a similar sort of ballpark regarding protection compared to the monovalent vaccine. But when it comes to severe disease, there isn’t any evidence showing the bivalent vaccine is superior to a boost with the monovalent vaccine.”
This, he said, is especially important in the South African context where nearly three-quarters of the population has been infected with the Omicron variant, “which itself would induce an immune response somewhat slanted in protecting against future variants of Omicron”.
A recent study published in the New England Journal of Medicine found the effectiveness of the original (monovalent) booster against severe Covid-19 was about 25%. The effectiveness of the bivalent booster was 62%. Overall, the bivalent shots were 37 percentage points more effective at preventing severe Covid-19.
Effectiveness was similar between the two different brands (Moderna and Pfizer), and whether or not people had received one or more boosters previously. Protection from both shots peaked at about four weeks, after which immunity waned.
While there was generally positive reaction to the results, Madhi said there were problems with the study design regarding the timing of the booster shots.
When to get a booster?
To truly benefit from the boost, he added, especially in protecting against mild-to-moderate Covid-19 disease, you need to time the boost to coincide with an upswing in the number of cases and with the next wave. “So if you boost now with the monovalent vaccine and the next wave occurs only 20 weeks from now, you won’t benefit much at all in being protected against mild-to-moderate disease, because by then the antibody would have waned.”
While Madhi would not insist on the bivalent vaccines, he said the reason the department is not buying the vaccine was probably because “they’ve got a massive surplus of monovalent vaccine that’s going to expire and it’s (the bivalent boost) going to be an additional cost.”
He added that the US CDC’s decision to recommend the bivalent vaccine “to all and sundry” was more of an anomaly rather than the norm. The focus of the UK and the WHO is primarily on boosting high-risk individuals.
“It’s difficult to understand what (the) US is trying to achieve by just asking everyone to be boosted with the bivalent vaccine,” he said.
“More importantly, South Africans over 60, especially those with underlying health conditions who have not had their fourth dose, should get it as soon as possible. The evidence is clear that a fourth and fifth dose increases protection in this age group.”
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