Additional COVID-19 vaccine boosters are not recommended for people at low to medium risk of the disease who have been vaccinated and boosted once, according to the World Health Organization’s (WHO) Strategic Advisory Group of Experts on Immunization (SAGE).

SAGE recommends an additional booster six to 12 months after the last dose for “high priority” people, depending on factors such as age and immuno-compromising conditions.

It defines the high-priority group as older adults, adults with significant comorbidities (eg diabetes and heart disease); those with immunocompromising conditions, including children from six months and older (eg people living with HIV and transplant recipients); pregnant women and frontline health workers.

New SAGE chair, Finland’s Dr Hanna Nohynek, said that the recommendations were “updated to reflect that much of the population is either vaccinated or previously infected with COVID-19, or both”.

“Countries should consider their specific context in deciding whether to continue vaccinating low-risk groups, like healthy children and adolescents, while not compromising the routine vaccines that are so crucial for the health and well-being of this age group,” she added.

SAGE, which met last week, also stressed that its recommendation for additional boosters applied in the current context only, and was not a recommendation for annual COVID-19 vaccine boosters.

It also urged countries to base decisions to continue vaccinating the low-priority group, primarily healthy children, on disease burden and cost-effectiveness “considering the low burden of disease” in this group.

This comes as vaccine manufacturers prepare to hike the cost of vaccines. Moderna and Pfizer are both planning an price increase of around 400% – from around $26 directly to the US government to $130 for the private market when government-sponsored vaccines are phased out.

Measles concern

Nohynek noted that every region of the world was reporting measles outbreaks, an indication that routine vaccinations for children had slipped during the COVID-19 pandemic.

SAGE will be reviewing the evidence “for vaccinating infants below six months and during pregnancy” which might lead to policy change, she added.In 2021, an estimated 25 million children missed their first dose of the measles vaccine, the worst level since 2008.

Impact of malaria vaccine

Dr Kate O’Brien, WHO’s Director of Immunization, Vaccines and Biologicals, said that the introduction of the RTS,S malaria vaccine in some of the worst affected malaria regions in Ghana, Kenya and Malawi, had resulted in a 10% reduction in all-cause mortality among children eligible to receive the vaccine.

“This is really a very remarkable impact of introducing this vaccine,” said O’Brien, stressing that it was only being introduced in areas with very high malaria rates.

However, there is high demand for the vaccine, with at least 28 countries expressing interest in introducing the vaccine, but supply remains highly constrained. For that reason, SAGE recommends flexibility in the immunization schedule in interval between the last two doses.

Four doses are currently indicated for children, from five months of age with doses administered monthly. 

The new R21/ Matrix-M malaria vaccine developed by Oxford University, “is in the late stages of clinical development, and we hope to review the final file in the coming months”, said Nohynek.

Identifying priority pathogens for new vaccines

WHO is in the process of defining regional priority targets for new vaccine development for non-epidemic pathogens. 

Early results indicate that tuberculosis, HIV, and antimicrobial-resistant pathogens such as Klebsiella pneumonia are important across all regions. Streptococcus pyogenes (Group A), Shigella, and respiratory syncytial virus (RSV) were identified as important by four or more regions, as was Plasmodium falciparum (malaria) by the African region.

There are “several candidate vaccines for TB in late-stage clinical trials” with the potential for multiple vaccines to receive regulatory authorization within three years, according to SAGE.

The candidate vaccine M72/ AS01E is showing the most promise 

Image Credits: Samy Rakotoniaina/MSH.