The international charity Medecins Sans Frontieres urged drugmakers GlaxoSmithKline and Pfizer on Tuesday to slash the price of their pneumococcal vaccines to $5 per child in poor countries.

In a report on vaccine prices ahead of an international donor conference in Berlin at the end of January, MSF slammed Big Pharma companies and said the cost of vaccinating a child in the world's poorest countries was now 68 times higher than in 2001.

The "skyrocketing" prices mean many countries can't afford expensive new vaccines such as those that protect against pneumococcal disease, which kills about a million children a year, MSF's report said.

"A handful of big pharmaceutical companies are overcharging donors and developing countries for vaccines that already earn them billions of dollars in wealthy countries," said Rohit Malpani, policy and analysis director for MSF's access campaign.

Responding to the criticism, GSK said in a statement that it was already barely covering its costs with the price it charges poorer countries for its pneumococcal shot, Synflorix, which it said was "one of the most complex we've ever manufactured".

"Many of our available vaccines are advanced and complex and require significant upfront capital investment to make and supply," it said, adding that to discount pneumococcal vaccines further would threaten GSK's ability to supply them long-term.

Pfizer also said its pneumococcal shot, Prevenar 13, was highly complex. "It takes more than two years to create one batch of Prevenar 13, encompassing some 500 separate quality control tests ... multiple facilities and hundreds of trained professionals," it said in a statement.

MSF's report said pneumococcal shots alone accounted for about 45 percent of the cost of fully vaccinating a child against 12 diseases. It said GSK and Pfizer had together reported more than $19 billion in global sales for pneumococcal vaccines since their launch.

A pledging conference for the GAVI global vaccines alliance is due in Berlin next week, when government donors and private philanthropists will be asked for some $7.5 billion to help immunize hundreds of millions of children in poor countries between 2016 and 2020.

"Governments need to put pressure on (drug) companies to offer better prices to GAVI," said Kate Elder, an MSF policy adviser.

"We need to put public health before profit. Life-saving vaccines for children shouldn't be big business in poor countries."