Specific considerations must be taken regarding transport of vaccines and coolant packs when organising mass vaccination campaigns. In such events, numerous teams deploy simultaneously to different vaccination points carrying their own passive cold chain means. The number and rotation of coolant packs and the freezing capacity of the active cold chain must be carefully planned as the ice-pack turnover will be very high, and the period for their reconditioning can last more than 24 hours.
The number of icepacks and the freezing capacity of our cold chain, is calculated based on 3 variables: the number of vaccination teams simultaneously deployed, their expected daily vaccine consumption (doses/day), and the duration of the campaign. The expected daily consumption of vaccines for a vaccination team determines the required transport capacity for a team, and is based on its expected performance: the expected number of people to be vaccinated each day.
The performance of a vaccination team depends on the flow of people through the vaccination site, the number of working hours, and the number of vaccinators and vaccine preparers in each team. Though this will depend enormously on the environment (rural/urban), the organisation of the vaccination site, and the number of vaccine preparers per vaccinator, with a steady flow of people, one vaccinator can vaccinate on average 1 to 3 people per minute.
Based on the expected performance for a vaccination team, the number of cold boxes, vaccine carriers and icepacks per team is calculated. To calculate the number of icepacks, consider the cadence for its replacement: depending on the weather conditions and handling habits, icepacks in the cold box will need to be replaced daily or every 2 days, and extra icepacks for vaccine carriers may be needed throughout the day.
Next step is to define the quantity of freezers available for the vaccination campaign and determine if they have enough freezing capacity and storage capacity. The (water pack) freezing capacity is normally measured in kg of ice produced in 24h. And the freezer volume is normally provided in litres or in number of coolant packs of a certain volume that can be loaded in it. This information is part of the freezer technical specifications. Freezers powered by mains, depending on their volume and performance, may have a water-pack freezing capacity ranging from 7 kg to 40 kg per 24 hours. Standard SSD freezers may have considerably less water-pack freezing capacity: around 2 kg per 24 hours. If, for example, a particular freezer has storage capacity for 160 water-packs (0.6 L), and a water-pack freezing capacity of 7.2 kg per 24 hours, it will take approximately 13 days to freeze a full load of water-packs.
Taking into account the number of icepacks needed daily by the vaccination teams, and that the returned icepacks of the day won't be ready after a certain time (depending on the freezing capacity), a stock balance must be calculated and projected throughout the whole vaccination campaign. This will help to determine the minimum initial stock.
The figure below shows an example of the stock management of ice during a 15 days mass vaccination campaign with a total freezing capacity is 250 kg per 24 hours.