Even after Pfizer and GlaxoSmithKline offered up pneumonia vaccine pricing concessions last fall, Médecins Sans Frontières isn’t letting up in its public pressure campaign against the drugmakers. The global charity took to social media on Valentine’s Day to call for further price reductions in developing countries.

In a series of Tweets and Facebook posts on Tuesday, MSF and its employees called on Pfizer and GSK to lower the price of their shots to $5 for all three doses in developing countries so children may have lifesaving access where they currently do not.

Kate Elder, Vaccines Policy Advisor at MSF, told FiercePharma the posts were part of the group’s long-term efforts to bring prices for the vaccines down. GSK markets Synflorix and Pfizer sells Prevenar, by far the world’s bestselling vaccine.

Last fall, after years of protests by MSF, Glaxo and Pfizer pledged to lower their vax prices during humanitarian emergencies, but those reductions haven’t yet materialized, Elder said.

"This is still being worked on months later," she said. "Children in emergencies do not have access to that vaccine. All of the contracting and legal work is taking place ahead of time."

Going forward, MSF plans a "number of actions" in the coming months to keep up the pressure, Elder said, in order to "let the companies know we are still watching them." They include World Immunization Week in April and the World Health Assembly in May.

"We are working with governments to prepare for those events," Elder said.

A Pfizer spokesperson said the company set up an Advance Market Commitment program in 2010 through Gavi, the Vaccine Alliance. Since then, more than 40 countries have established pneumococcal immunization programs, she said.

Even still, the company is aware of the challenges in countries that aren’t eligible for purchasing through Gavi. Pfizer is "working to identify ways in which we can work with those governments to further refine our pricing and access approach to meet their needs," she said.

Meanwhile, the New York drugmaker reported a significant slowdown with its key Prevenar franchise in the fourth quarter. Sales for the shot were down 25% versus 2015, missing Street estimates and dragging on the company’s vaccines sales for the period.

Previously, Pfizer offered up a million Prevenar doses for donation, which MSF denied on grounds they wouldn’t ensure long-term access.

When asked to comment on the renewed push by MSF, a GSK representative pointed to Glaxo’s September statement about Synflorix pricing for refugees.