Cold Chain Problem for Vaccines - Silk Worms can Help!

-->

The elimination of serious infectious diseases such as small pox and polio requires immense international collaborative effort. The World Health Organization, UNICEF, the Rotary Foundation, the Bill and Melinda Gates Foundation and many other groups are currently working on a number of infectious diseases, such as polio, tuberculosis, HIV/AIDS and diarrheal diseases.   Small pox was successfully eradicated in 1977, a momentous victory that required decades of work.   For polio and other serious infectious diseases, problems in poor countries include wars, lack of basic health infrastructure, lack of roads and electricity, ignorance and suspicion of the West, and anger stemming from the purported misuse of a Hepatitis B immunization program in Abbottabad to obtain DNA samples from suspected relatives of Osama bin Laden.  Workers bravely carrying out immunization campaigns in Pakistan, despite a fatwa from Islamist groups prohibiting vaccination, were killed in December 2012, and again January of 2013. Nine workers giving polio vaccine were killed in Nigeria in February, 2013.  Nigeria, Pakistan and Afghanistan are the only countries still reporting cases of polio. In resource-poor countries infectious diseases make up more than half of all deaths, and those who most need effective vaccines and antibiotics may not get them.  Measles is a leading killer of children worldwide, and can be prevented by vaccine, when and if it is available.

One of the problems with vaccination campaigns is the need to keep vaccines cold, when transporting them in hot areas which lack refrigeration and electricity. High temperatures are found to destroy almost half of the vaccines produced around the world.  Polio vaccine must be kept at 35 to 46 degrees F for vaccination to be successful.  Antibiotics and other medications also need to be protected from heat. According to the World Health Organization (WHO), as recently as 2008, almost half of all vaccines delivered to developing countries were ruined due to poor cold chain services. Further, cold chain “breaks” lead to ineffective vaccines being administered with a consequent loss of life and lack of vaccine compliance.

  Researchers at Tufts University have found that vaccines and other drugs can be stabilized in silk protein made from silkworm cocoons, enabling them to withstand temperatures as high as 140 degrees F for over 6 months.  They start with silkworm cocoons, boil them with sodium carbonate to separate a protein called fibroin, mix this with salt, then mix it with the substance to be preserved (the vaccine, or drug) and spread the result out as films, then freeze-dry it.  The films contain a fibroin matrix filled with tiny pockets that contain the medicine.  They are surprisingly stable for up to six months, regardless of temperature.  Silk protein is acceptable to the human body, used in wound closure, and may even have wound healing properties that are under investigation.  It can be taken orally without problems. Ultimately, substances made from silk may be used to replace a vein or a bone in the human body.  Tufts researchers note that silk protein can be used as packaging, for food and other products, thereby eliminating some of the problems of plastic use and disposal.

A team of four students from Harvard started a company, Vaxess Technologies, that is producing the new products, vaccines and medications, incorporated in silk fibroin.  In cooperation with the Tufts professors who developed the new silk technology, Vaxess hopes to have a product that will solve the cold-chain problem within a few years.  You can watch interesting videos on the new silk technologies presented by David Kaplan and Fiorenzo Omenetto (professors at Tufts) on TED or youtube.

Sadja Greenwood, MD, MPH   See other columns on this blog