The results of GlaxoSmithKline’s final study on the world’s first malaria vaccine show that the drug is only partially effective, working in about one-third of all cases. Considering that over half a million people die from the disease every year, the company is still working to get the vaccine RTS,S approved for use, with the idea that saving some lives beats saving none.

In the study, now published in The Lancet, results show the drug failed to be 50 percent effective in the most recent clinical trial, missing the mark set by the World Health Organization, Sky News reported. The trial spanned over three years and involved the immunization of 15,500 babies and toddlers with the vaccine. One group received three doses of the vaccine, the second also received a booster shot, and the third group got a placebo shot. All the children slept with a mosquito net and were followed up for four years.

Results showed that the vaccine was only about 30 percent effective, with those who received both RTS,S and a later booster shot having the highest level of protection. The vaccination was slightly more effective when administered within 5 to 17 months of age, but made no difference in the severity of malaria or the likeliness of dying from the disease. The most common side effects of the vaccine were pain, fever, and convulsions, but meningitis was reported in 22 cases, although researchers are not sure why.

The World Health Organization will meet in October to decide whether or not the vaccine will be used. Most vaccines, such as that for measles and polio, work up to 90 percent of the time, and some believe that the malaria vaccine’s low effectiveness may inhibit some parents from vaccinating their children in the first place.

“This vaccine could mean children will have only two bouts of malaria a year instead of five," said Dr. Martin De Smet, a malaria expert at Doctors Without Borders who was not connected to the study, Sky News reported. "They know their child will probably get some malaria despite the vaccination, so how enthusiastic are they going to be?”

Others feel that it’s still a major medical breakthrough and worthy of real-world application.

"It's not good enough to stop transmission, but it will cut the huge burden of disease," Dr. Brian Greenwood, the lead author on the study explained, as reported by Sky News. "Preventing some of those attacks is not insignificant."

Malaria is a life-threatening disease caused by parasites transmitted through the bite of a mosquito. Symptoms of malaria include fever, headache, chills, and vomiting. According to the World Health Organization, around half of the world’s population is at risk of malaria. Of those who contract the disease, death is most common among children living in Africa. Global death rates from malaria have dropped 47 percent since 2000, but still each year an estimated 584,000 people die from the disease.

Source: Greenwood B, et al. Efficacy and safety of RTS,S/AS01 malaria vaccine with or without a booster dose in infants and children in Africa: final results of a phase 3, individually randomised, controlled trial. The Lancet. 2015.