New Delhi, Aug 15 : Trials of an experimental malaria vaccine have shown promise to protect mothers from malaria during pregnancy, according to the US National Institutes of Health (NIH).

Malaria parasites are spread by Anopheles mosquitoes, including those of the species Plasmodium falciparum (Pf). While it can cause illness in people of any age, pregnant women, infants, and very young children are particularly vulnerable to life-threatening diseases.

An estimated 50,000 maternal deaths and 200,000 stillbirths occur in Africa every year due to malarial parasitemia in pregnancy.

The trials showed that the PfSPZ vaccine -- a radiation-attenuated jab based on Pf sporozoites (a stage of the parasite's lifecycle), and manufactured by US-based biotechnology company Sanaria, was efficient and did not require a booster dose -- a first for any malaria vaccine.

One of the trials enrolled 300 healthy women ages 18 to 38 years who anticipated becoming pregnant soon after immunisation.

The women were administered with the drug treatment to remove malaria parasites, followed by three injections spaced over a month of either saline placebo or the investigational vaccine at one of two dosages.

Women who took both dosage of PfSPZ vaccine had a 'significant degree of protection from parasite infection and clinical malaria that was sustained over a span of two years', even without a booster dose, said the researchers, from the NIH's National Institute of Allergy and Infectious Diseases (NIAID) and the University of Sciences, Techniques and Technologies, Bamako (USTTB), Mali, who co-led the trials.

The trials, published in the journal The Lancet Infectious Diseases, showed that 55 women became pregnant within 24 weeks of the third vaccine dose. Among these women, vaccine efficacy against parasitemia (whether before or during pregnancy) was 65 per cent in those who received the lower dose vaccine and 86 per cent in those who received the higher dose.

Among 155 women who became pregnant across both study years, vaccine efficacy was 57 per cent for those who received lower dose vaccine and 49 per cent for those in the higher dosage group.

Women who received the vaccine at either of the dosages also conceived sooner than those who received a placebo. However, this finding did not reach the level of statistical significance, the team said.

The researchers speculate that the PfSPZ Vaccine might avert malaria-related early pregnancy losses since parasitemia risk during the periconception period was reduced by 65 to 86 per cent.

'If confirmed through additional clinical trials, the approach modelled in this study could open improved ways to prevent malaria in pregnancy,' the researchers said.

/IANS