Refrigeration for vaccines is still a major barrier to boosting vaccination rates and lowering deaths caused by preventable diseases in many parts of the developing world. But a new study by Médecins Sans Frontières shows that some vaccines can be used safely outside the cold chain, underscoring the need for more research on heat-stable vaccines.
"If more vaccines could be safely used outside of the cold chain for a period of time, particularly for the last stretch of their journey to people living in the most remote areas, we'd be able to reach far more children," said Dr. Greg Elder, deputy director for operations at MSF, in a statement.
A growing body of research has shown that some vaccines can leave the cold chain for a short period just before they're used and still be safe and effective. This so-called 'controlled temperature chain' (CTC), or flexible cold chain, would help ease the logistical problems that come with transporting vaccines in the last leg of their journey to remote areas with little access to refrigeration. The World Health Organization has so far only recommended one vaccine for use in CTC conditions--the meningitis A vaccine MenAfriVac, which was approved in 2012 for up to four days at up to 40⁰C, or 104⁰F.
A new study by MSF's Epicentre shows that one tetanus toxoid vaccine can also be safely used in CTC conditions. Epicentre studied the efficacy of the Serum Institute of India's tetanus toxoid vaccine when kept in a controlled temperature chain at temperatures of 40⁰C for up to 30 days after they're shipped. Cold chain standards require vaccines to be kept between 2⁰C and 8⁰C, or 35.6⁰F and 46.4⁰F, from the time they are manufactured until they meet the recipient. In two groups of women in Chad who received the vaccine, either after being kept in a strict cold chain or out of the cold chain for up to 30 days, both groups of women were adequately protected against tetanus, the study found.
"In the immediate term, the onus is on the pharmaceutical companies to generate data and take the initiative with regulatory bodies so that their vaccines can be relicensed for use outside of the strict cold chain," said Dr. Rebecca Grais, director of epidemiology at Epicentre, in a statement. "Longer-term we want the next-generation vaccines to be developed and licensed with ambitious heat stability targets so that this problem is avoided from the outset."
- read the issue brief from Médecins Sans Frontières (PDF)
- and see the MSF statement