Vaccine Cold Chain and VVM, ensuring the potency of vaccines

Vaccine Cold Chain and VVM, ensuring the potency of vaccines

Responsible parens take their children to the nearest hospital for vaccination. Vaccines are readily available there. The only thing that bothers the parents is about the injections being painful and the possibility of developing fever after taking the shot. Has anyone of you thought about the potency and effectiveness of the vaccines that are available at the hospital in your area? Did you know that most of the vaccines used these days are sensitive to heat?

What benefit is there if the vaccines that are being given to the children are not effective? Just think about it.

But, don’t worry. At government hospitals in India, where the Immunization programmes are being conducted very effectively, correct measures are adopted to ensure the potency and effectiveness of every single vial of vaccine that is being used. I can say this, because I’ve been working in a government owned public hospital for the past 3 years now. I’ve written several articles on vaccines and vaccination programmes in this blog before. You can find them by clicking here.

Now, coming back to our topic, I had just mentioned that all government hospitals are strictly following certain policies by which the safety and effectiveness of vaccines are safeguarded. I’m not saying that the private hospitals are not following these policies, but I strongly doubt it. I’ll tell you why I think so later.

In this article I”ll tell you about the cold chain storage and transport system for vaccines, the vaccine vial monitors and lastly on why you can vaccinate your children with confidence at government hospitals.

The Vaccine Cold Chain

Cold chain is the system of distribution of vaccines from the manufacturer to the beneficiaries in a potent state keeping the required temperature.

The cold chain is actually the backbone of the immunization programmes in India as well as all over the world.

The successful implementation of a vaccination programme actually depends on how effectively the cold chain system is being maintained.

Why Cold Chain?

Some vaccines are heat sensitive. Their potency and life is reduced when they are exposed to heat. I’m talking about normal room temperature here and not the real heat. Vaccines therefore needs to be stored in cool conditions to increase their life as well as potency.  For example, polio vaccine is the most sensitive vaccine to heat, whereas Tetanus vaccine is the least sensitive to heat.

In a country like India, the economical constraints should also be taken into consideration while planning and conducting vaccination programmes. Most of the vaccines included in the Universal Immunization Programme are costly. The only way to make maximum possible use of these costly vaccines is by keeping them potent for a longer time. This can be done by storing and transporting the vaccines at a recommended minimum temperature.

The Equipments of Vaccine Cold Chain

The potency of vaccines are ensured and their shelf life is increased by treating vaccines as “cold cargo” from the site of their manufacture to their use at the rural peripheries. The following instruments are used in the vaccine’s cold chain :

Refrigerated Truck – For the transport of vaccines from manufacturer to regional stores or airports/seaports.

Vaccine delivery van – For transport of vaccines from airport/seaport to district stores, and for distribution of vaccines to various storage centres including hospitals. Cold boxes should be used while transporting vaccines in these vehicles. For transporting vaccines from health centres to the subcenters or anganwadis where vaccinations are given, any four wheeled vehicle can be used provided that the vaccines are transported in cold boxes or vaccine carriers to ensure their potency.

Walk-in Coolers and Freezers – For bulk storage of vaccines at manufacturer’s store or regional stores. Walk-in coolers maintain a temperature of 4 to 8 degree celsius whereas walk-in freezers are maintained at -20 to -18 degree celsius. These freezers and coolers are built in with modern temperature recorders, alarms and can even handle unexpected power failures.

Deep Freezers – Freezers of large and small sizes are used at large stores and health centres respectively in order to store the two most heat sensitive vaccines namely, oral polio vaccine and measles vaccine. These freezers are also used to freeze ice-packs. Daily temperature recording of these freezers are done.

Ice Lined Refrigerator  – Specialised vaccine storage refrigerators used at health centres. Temperature is recorded daily.

ilr vaccine cold chain
Ice lined refrigerator for storing vaccines

Cold box – For transport and short time storage of vaccines using ice-packs which are first placed inside the cold box.

cold box vaccine
Cold box for transporting vaccines

Vaccine Carrier – To carry vaccines from health centre to vaccination site. Two or four ice packs can be placed in these vaccine carriers depending on the number of vaccine vials that are to be transported.

Other Equipments – Ice packs, voltage stabilizers, dial thermometers, temperature recording book

It should be noted that any compromise made in any one of the above equipment’s maintenance breaks the cold chain which in turn makes the vaccines inactive. Only trained healthcare workers can properly maintain a good vaccine cold chain.

Vaccine Vial Monitor (VVM)

Now, how can you make sure that the hospitals in your area are properly maintaining the cold chain? Is there a way to find out whether the vaccines are still potent and effective as they were at the time of their manufacture?

Here is where a revolutionary invention comes handy. In developing countries like India, the chances of breaking a cold chain is very high. The cold chain may not be preserved in the distribution of vaccines in many parts of the developing countries. The vaccines in these circumstances would be inactive and ineffective. In 1996, the introduction of the Vaccine Vial Monitor (VVM) became a turning point in the vaccination programmes all over the world.

A vaccine vial monitor (VVM) is a thermochromic label put on vials containing vaccines. It gives a visual indication of whether the vaccine has been kept at a temperature which preserves its potency.

How to use the VVM?

Image courtesy – PATH, the founders of VVM

The vaccine vial monitor consists of a heat sensitive square within a circle. All you need to do is to look for the colour of the square part compared to the circle. Normally, the square is white in colour and the circle surrounding the square will be light blue (or grey) in colour.

If the monitor is exposed to heat, it changes colour with time. The colour changes with increasing speed in hotter conditions. If the square becomes the same colour as the circle or becomes darker than the circle, then the vaccine contained in the vial (on which the VVM label is affixed) is damaged. Such inactive and damaged vaccine vials should be discarded.

Now, whenever you are in doubt about the safety and potency of vaccines, you know where to look for.

Some of the most common vaccines for which the VVM is used include :

  • Oral Polio Vaccine
  • Hepatitis B vaccine
  • Pentavalent vaccine
  • DPT vaccine
  • Measles vaccine
  • MMR vaccine
  • BCG
  • Tetanus vaccine
  • Today, the World Health Organization recommends that every vaccine supplied via the UNICEF should have a VVM.

The VVM is another strong reason why the Pulse Polio Programme has become a huge success in making India a “polio free” nation.

It’s estimated that VVMs will allow workers to recognize and replace more than 200 million doses of damaged vaccine and to confidently deliver more than a billion more doses in remote settings—saving lives and reducing illness for countless people.

Why I recommend Government Hospitals for Vaccinations

A well maintained cold chain and the vaccine vial monitor are two of the most important reasons why I recommend you to vaccinate your children at Government hospitals. I would be surprised if any of these measures are being followed at the private hospitals in India. Most of the private hospitals store vaccines in household refrigerators and that too in the refrigerator door. Pharmacies and medical shops in India where these vaccines are readily available at a higher cost are not even keeping the requisite standards needed to ensure it’s potency. At the same time, you are getting good quality vaccines free of cost at government hospitals. Lack of trained healthcare professionals in the private sector is also another big factor to be considered. Next time you visit a hospital for vaccination, just ask the nurse about VVM and cold chain. You’ll get a satisfactory answer from a government hospital staff, but I’m not so sure about the private hospitals.

I’ve been to many hospitals and i can confidently say that I’ll vaccinate my child only at a government hospital. What about you?

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2 thoughts on “Vaccine Cold Chain and VVM, ensuring the potency of vaccines”

  1. Hi Dr Prasoon,

    I have noticed that the vaccine chart followed by government hospitals is different from the ones followed by private hospitals. Which one is better to follow.


    • Good Question There. Well, only two or three vaccines are given extra at private hospitals. PCV, Rotavirus vaccine are the two most important ones that are not yet available at government hospitals. For my one year old son, I gave him all the vaccines that were available at our PHC and then bought the PCV from outside. It was also administered at the government hospital but I had to buy it from outside.. I prefer the government vaccines because I’m pretty confident about the cold chain system and the satisfactory vaccine potency for the vaccines transported and delivered throught the government system. You can always opt for the private hospital vaccines, but you’ll have to pay for each and every vaccine they give. Hope your doubt is cleared.

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