A vaccine against malaria could be introduced in the world's worst-hit countries in 2015, after the latest trial of a treatment produced by Britain's biggest drug company reduced the number of cases of the disease experienced by babies.

The results of trials published on Tuesday in Durban, South Africa, showed that the RTS,S vaccine developed by GlaxoSmithKline nearly halved the cases of malaria experienced by children aged between five and seven months and cut the number of cases in babies aged 6 to 12 weeks by a quarter.

The treatment's protection lasted for 18 months, although it waned slightly over time, and while that is not the sort of efficacy that parents in Europe or the US are used to getting in the vaccines given to their children, the malaria vaccine would make a significant difference to the outlook for those in areas where the tropical disease is rife.

Every year, around 660,000 people die from malaria, most of them small children under the age of five. There are about 219m cases of the disease a year worldwide, and children who survive the serious illness can suffer damage to their health and development in their lifetime afterwards.

Sir Andrew Witty, chief executive of GSK, said the company was very encouraged by the latest results and would now apply for a regulatory licence for its use in Africa under a special provision of the European Medicines Agency. "While we have seen some decline in vaccine efficacy over time, the sheer number of children affected by malaria means that the number of cases of the disease the vaccine can help prevent is impressive," he said.

Duncan Learmouth, GSK's senior vice- president for developing countries and market access, said that if malaria were as serious a problem in the UK as it was in Africa, the company would be seeking a licence for this vaccine in spite of its limited efficacy.

"I'm not sure it would be different if the impact of the disease was as it is in Africa. If we were looking at a disease in Europe and the US that had a similar clinical impact and burden on the health services, I actually think we would be pressing ahead for this," he said.

Inventing a malaria vaccine has involved breaking new medical ground. This is the first-ever vaccine against a parasite, said Learmouth. There are other novel vaccines in development, such as one from the US that involves injecting patients with weakened parasites, but Learmouth insisted GSK was not rushing to get a licence because it feared competitors.

"We're really not. I think the nearest vaccine is still in phase one – there is a huge long way to go. This is a very complex area. I don't expect a competitor vaccine for a very long time," he said.

GSK says the vaccine will be not-for-profit – but it will add 5% to the cost price which will go towards further research and development work on tropical diseases. The pharmaceutical giant has spent $350m (£218m) on the vaccine so far and expects to invest $260m more before it reaches children. A team of 40 people will be needed to process the 1m pages of paperwork out of the many trials, which were held in seven Africa countries in different age groups. The Bill and Melinda Gates Foundation also put in about $200m.

The dossier will go to the European Medical Agency next year and if it gets its licence, will go to the World Health Organisation for approval. It is expected that the donor-funded GAVI – the Global Alliance for Vaccines and Immunisation – will eventually pick up the bill for vaccine programmes as the treatment is deployed in malarial countries. Because the vaccine appears to be more effective in infants from five months of age, it may not be given at the same time as the basic immunisation for babies, such as diphtheria, whooping cough and tetanus, but later, like measles and pneumococcal vaccine. The introduction of a booster jab, at 18 months, is now also being trialled to see if it can increase the duration of the vaccine's protection.

The treatment was developed with the US-based non-profit PATH Malaria Vaccine Initiative. David Kaslow, vice president, product development at PATH, said the limited efficacy of the vaccine must be put in context. There has been great progress with bed nets and other technical measures, "yet there is still a huge disease burden out there", he said. In that context, the vaccine has "a potentially significant public health impact". During the trials, he pointed out, there were 941 cases of malaria averted for every 1,000 children vaccinated.

Dr Lucas Otieno of the Kenya Medical Research Institute-Walter Reed Project, who has been involved in the trials from 2005, cautioned that the good medical care that all participating children were given – they were seen by doctors as soon as any symptoms developed – may have prevented many malaria cases becoming serious. So it was possible, he cautioned, that the vaccine was more effective than appeared in the trials. However, Otieno added that there had been no shortage of volunteers for the trial from families for whom malaria was a permanent fear. "The volunteers were keen across all the sites," he said. "In my site, we had 1,631 children and we recruited the initial 1,000 within about three months, which was very impressive."