Many of us are familiar with vaccines. In the US where I live most of us have been vaccinated for major diseases such as whooping cough, Hepatitis A, measles, mumps, rubella, tetanus, diphtheria, the list goes on. However, due to our developed infrastructure and relative ease of access to medical care many of us have never worried about obtaining vaccines for our children or ourselves. This alone has contributed to some of the most startling gains in public health that we’ve ever seen.
In other parts of the world though, this is a very different story. Less infrastructure and fewer opportunities for medical care has made vaccinating large segments of the human population extremely difficult with serious consequences for those who are not vaccinated.
One major hurdle in the race to vaccinate the majority of people on this planets is the maintenance of cold-chains for vaccine delivery.
A major factor for making sure that vaccines retain their efficacy is to store them properly. This means keeping vaccines refrigerated until they are ready for use. A cold chain refers to the series of refrigerated environments that the vaccine must be transported and stored in. These vaccines must be kept between 35- 45° F (2-8° C). Now imagine trying to do this in remote areas in Nigeria or Pakistan, where temperatures can regularly reach 90° F (32° C) and refrigerators can be hard to come by. Add to this the fact that many vaccines cannot be frozen and maintaining this temperature range becomes even more difficult.
Storage conditions are so critical because once a vaccine loses its activity it cannot be restored. If this vaccine is then used for immunization those treated will not develop immunity and all the energy spent getting these vaccines into the field if for naught.
Thankfully, due to improved cold-transport techniques such as better insulation and cold-packs it is quite possible to get vaccine to storage facilities in remote areas. See the image below for an example of one of these cold chain packages containing cold-packs and multiple vaccines for delivery to Mozambique in Africa.
Additionally, advances have provided field health workers with temperature-sensitive stickers that can be adhered to the vaccine vials. These stickers (known as Viral Vaccine Monitors, or VVMs) will change color if the vaccine reaches a temperature outside of the accepted safe range of 2-8° C. Simple advances such as this make sure that only effective vaccines are used and also reduce waste by allowing health care workers to easily determine if the vaccine is still good or if all of their samples must be thrown away after an event such as a power outage. This occurred in 2006 in Indonesia after a massive earthquake shut down power at many clinics across the country. Despite the loss of power, the vaccines were determined to be usable due to the VVM sticker, thereby saving around 50,000 doses of vaccine.
Advances such as VVM as well as improved access to electricity and refrigeration have been major steps in delivering potent vaccine to those in need, but the difficulties inherent in this are still very much present. Not all areas have electricity, and in other areas power is intermittent and can go down for days, making storage after arrival uncertain.
New vaccines are being developed to get past this hurdle. By making new vaccines that are more temperature stable we can ease cold-chain requirements and get more vaccine to those who need it the most. Even some novel vaccine ideas have been suggested, such as the antigen-in-bananas that I’ve mentioned previously.
These advances are still very much necessary, as our ever-expanding human population requires more vaccines to keep fatal diseases at bay. Challenges like this will not go away through ignorance as we have to accept the reality of the conditions with which we must work. Expanding populations in tropical regions where fatal diseases still reside are part of what we have to deal with in the coming decades and we need to act accordingly in order to keep these diseases at bay. This can be done, but will require the concerted effort between the scientific community, public health organizations, and the general public.
Guidelines for maintaining vaccine cold chain
Safe Vaccine Handling, Cold Chain and Immunizations by W.H.O.
Not too hot, not too cold: Protecting lifesaving vaccine from freezing or heat damage