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Global Maternal Strep B Immunisation Could Save Lives

A global campaign to vaccinate pregnant women against group B Streptococcus (strep B) could prevent thousands of deaths globally and save millions in healthcare costs worldwide, according to computer modelling simulation research led by the London School of Hygiene & Tropical Medicine (LHSTM).

The researchers noted that Strep B infection in pregnancy could cause sepsis and meningitis in newborns, which sometimes led to death or disability, as well as increased risks of stillbirth and preterm births. 

Vaccines against group B Streptococcus (GBS) are not yet available but several are under development, and their potential health impact and cost-effectiveness have not been assessed globally, the researchers said. 

Cost-Effectiveness Modelled

The researchers used recent global estimates of the health burden of strep B in pregnant women and their children to estimate costs to healthcare systems, including calculated quality-adjusted life years lost due to infant mortality and long-term disability. They then modelled what would have been the cost-effectiveness of giving Strep B vaccines to 140 million pregnant women in 183 countries in 2020.

The model used World Health Organisation's (WHO) "list of preferred features for a Strep B vaccine" to make assumptions that such a vaccine could prevent infection in 80% of women vaccinated, and that women who attended at least four antenatal visits would agree to be vaccinated. 

Their study, published in PLOS Medicine, calculated that this could avert over 200,000 GBS cases and more than 31,000 deaths globally. Specifically, it could avert 127,000 (95% uncertainty range 63,300 to 248,000) early-onset and 87,300 (38,100 to 209,000) late-onset infant cases; 31,100 (14,400 to 66,400) deaths; 17,900 (6,380 to 49,900) cases of moderate and severe neurodevelopmental impairment, 23,000 (10,000 to 56,400) stillbirths, and 185,000 (13,500 to 407,000) preterm births.

Tiered Pricing Needed for 'Equitable Access'

Using differential costing of vaccine doses at $50 a dose in high-income countries, $15 in upper-middle income countries, and $3.50 in low- and lower-middle income countries, they estimated that globally, the value of an annual global maternal Strep B one-dose vaccination program ranged from $1.1 billion (95% uncertainty range: $-0.2 to $3.8 billion) to $17 billion ($9.1 to $31 billion), depending on the normative assumptions used by policymakers.

They also calculated that the costs of such a programme could be "partially offset by savings in healthcare costs, along with substantial health gains, notably reductions in morbidity and mortality", and estimated that it could save $385 million in healthcare costs. 

However, they cautioned that: "without tiered pricing, equitable access would likely not be achieved."

They acknowledged that the study was limited by "the scarcity of data to inform some of the model parameters", such as on the impact of Strep B on health-related quality of life and long-term costs of disability, and how these parameters might vary across country contexts.

The researchers concluded: "As vaccines get closer to approval, a global economic evaluation of vaccination will inform investment decisions in further vaccine development as well as guide fair financing and pricing."

First author Simon Procter DPhil, from the LHSTM, said: "By reducing severe GBS infections, an effective maternal GBS vaccine deployed worldwide could prevent tens of thousands of newborn deaths and stillbirths each year. Our findings suggest maternal vaccination against GBS could be cost-effective in most countries, and we hope this will encourage the further investment needed to bring GBS vaccines to market."

Asked to comment on the proposed vaccination campaign by Medscape News UK, Professor Hassan Shehata, consultant obstetrician and vice president of the Royal College of Obstetricians and Gynaecologists, said: "We are all too aware of the devastating consequences group B strep can have on babies both here in the UK, but particularly in low-income countries where screening is harder to routinely implement and antibiotic administration during birth not as readily available.

"We welcome the findings of this modelling, which suggest that maternal group B strep vaccination could prevent thousands of infant deaths and stillbirths, and be cost-effective to implement in most countries. We concur with the authors in hoping this will encourage investment in developing these much-needed vaccines."

SRP, BPG, PP, JC, FS, AK, JEL, and MJ were supported by funding from a grant to the London School of Hygiene & Tropical Medicine from the Bill & Melinda Gates Foundation. FS is employed by the UK NSC which developed the policy recommendation for maternal GBS screening. RH is member of the World Health Organisation.