POST 00218 : T-ZONES & LTP

Post0218 T-ZONES & LTP 18 January 2000 CONTENTS 1. T-ZONES AND LOW TEMPERATURE PROTECTION 2. VACCINE FREEZING AND FROST FREE REFRIGERATORS, CONTINUED 3. REFRIGERATOR TEMPERATURE RANGE 2'C TO 8'C? 4. SOLUTION SUGGESTION FOR VACCINE FREEZING 1.T-ZONES AND LOW TEMPERATURE PROTECTION Hans Everts, WHO/V&B, who was, unfortunately, unable to attend the Technet'99 meeting in Harare continues his update on outstanding Technet issues. This continues from TECHNET post0217 Fast Chain, 17 January 2000. Temperature regulation, LTP, and T-Zone testing, were discussed in TECHNET Post0123, T-ZONES & LTP & VVM, 12 March 1999, and continued the the discussions from Post0117, Post0116, Post0113, Post0111, Post0107 LTP, Post0104, and Post0102. Temperature zones [T-Zones] and low temperature protection for cold chain equipment specifications were agreed in principle at the Technet'98 meeting in Copenhagen. Hans, Terry Hart ITG/India, Anthony Battersby, FBA, and Allan Bass acted as a working group for this issue, with Hans also acting for the Technet Secretariat at WHO. In yesterdays TECHNET Post: " On other matters: You had planned to have the new PIS at the printers in December 1999. Is that done? I hope not - we did not discuss the need for mandatory low temperature protection - specifically 0'C cutouts. Soren Spanner posted something on that last week. I join him in feeling that this is an urgent matter." "regards, allan" Two files on the Temperature Zones are available for download via the web: ftp://ftp.acithn.uq.edu.au/Technet/1-ClickHereForTECHNETfiles/Coldchain/ Click on the files: NewTzonesJan2000.PDF details the proposed Temperature zones Diurnalcycle-xls.PDF contains the spreadsheet calculations of the dirunal cycle and world coverage. or get the file by by email to: [[email protected]][email protected][/email] with the message: get technet NewTzonesJan2000.PDF get technet Diurnalcycle-xls.PDF Action, comments and additions please: [[email protected]][email protected][/email] or use your reply button ___________________________________________________________________________ From: [[email protected]][email protected][/email] Date: Fri, 07 Jan 2000 15:16:53 +0100 To: Cc: [[email protected]][email protected][/email] Subject: T-Zones and Low Temperature protection Don't worry, work on the PIS will start in 2 weeks and take about 3 months. We have hired a person to work only on that. I agree the zero cut off need to be discussed, but I do not think that is an issue for the PIS, but for the specifications. We should have at some stage a smaller meeting to see what we do with the domestic refrigerator issue. I have made some progress on the temperature zones. Especially the calculation of the diurnal cycle has taken some time. Please post the attached files for comments. The determination of the diurnal cycle is based on the CD ROM of the World Meteorological Organization, with more than 30 000 data over the last 30 years. THE DIURNAL CYCLES PROPOSED ARE: Hot Zone: 43 - 25 Temperate Zone: 32 - 15 Cold Zone: 32 - 15 and 15 - minus 5 * For those who are interested, the calculation was done as follows: The WMO database provides for all stations the mean maximum and minimum temperature per month over 30 years. I have taken the difference between these 2 as the basis for the computation of the diurnal cycle. I did not attach the WMO file, because its size is 13 MB (Anthony, if you want I can send it to you). The average of all these differences gives the average diurnal cycle, which is of course not enough, since an average itself does not tell anything about the spread of the data. I assumed a normal distribution of the data, which turns out to be not far from the truth as can be shown in the small difference between the mean and the median. In a normal distribution the average plus/minus 2 times the standard deviation covers 95% of the measurements. Let's call this the diurnal interval. With an upper limit of 43?C or 32?C, the lower limit can then be determined by taking the diurnal interval (average difference plus twice the standard deviation) off. As you can see in the Excel file, this gives for all stations a lower test point of 24.77?C for the hot zone and 13.77?C for the temperate zone. If we would, for the sake of standardization, use 25?C and 15?C, we would still cover respectively 94.88% and 92% of the measurements for all stations. However, as you can see, the difference between maximum and minimum in Africa is bigger than elsewhere. To cover 95% we would have to take 22.57?C and 11.6?C as lower test points, which is a few degrees from the currently used standards. You can see that if we would use 25?C and 15?C we would only cover 84.44% and 76.6%, which as such would not be enough. I do not think we should go lower than 90%. However, there is an over-estimation in the calculations for 2 reasons: 1) the mean maximum and the mean minimum do not necessarily and probably will not often fall on the same day; 2) appliances are not directly exposed to the extremes of the diurnal cycle, which concerns outside temperatures. The fact that they are installed inside [a building] has an attenuating effect. I have assumed an attenuation of 3?C, which I think is not exaggerated. The last column shows the percentages of measurements covered, when an attenuation of 3?C is included, while respecting the lower limits of 25?C and 15?C. Even in Africa this brings the number of measurements covered easily above the 90%. To conclude therefore, I think it is justified to use in the [cold chain equipment] specifications, from now on, the diurnal cycles 43?C-25?C and 32?C-15?C, since this interval covers at least 95% of all measurements. regards, Hans --- From: Date: Fri, 14 Jan 2000 To: [[email protected]][email protected][/email] Cc: [[email protected]][email protected][/email] Subject: T-Zones and Low Temperature protection Dear Hans, Thanks! The Fast Chain posting should go out today or Monday. Thanks for doing all of the work on it. If I have any questions - I'll put it in the Technet post as well as email to your for your thoughts. * We do need to discuss the zero cut off specifications - and testing procedures. I suggest we draft something and put it to the forum in the next few weeks. I know there is a lot of grumbling because this has been on the agenda for so long without any action. After safe injections and VVMs, low temperature protection is, perhaps the key cold chain equipment issue relating to program cost effectiveness - in terms of human costs, vaccine costs, opportunity costs, and energy costs. * The reason I mentioned the PIS - it that I think that the advice on Low Temperature Protection should be in the PIS - as the cold chain reference manual - which is how it is used! (Glad you have some help on the PIS) * The other thing noted recently - is that some countries are using commercially marketed domestic picnic ice packs - which usually have additive salts and polymers to depress the melting point - increasing the potential for vaccine freezing. You will recall that WHO has the test reports on cold packs from the late 70's/early 80's. I think that these need to be re-issued - perhaps through the PIS. more later, regards and best wishes, allan ____________________________________*______________________________________ 2. REFRIGERATOR TEMPERATURE RANGE 2'C TO 8'C? The current WHO recommendation for EPI vaccine storage in refrigerators is for one month at 0 'C to +8'C. Other regions of the world and other countries recommend +2'C, or even +4'C to 8'C. Many manufacturers label their vaccine vial for storage between 0'C and 10'C. * Mary Catlin, PATH, proposes, considering the risk of zero degree storage on HepB - a vaccine coming into wide routine use, that we try to modify the recommendation to +2'C to Plus 8'C on the TECHNET Forum. The slop and hysteresis inherent in the cheap mechanical refrigerator thermostats that are in most refrigerators makes the 0'C recommendation a danger to freeze sensitive vaccines. Action, comments and additions please: [[email protected]][email protected][/email] or use your reply button ___________________________________________________________________________ From: "Catlin, Mary" To: "'Technet Moderator'" Subject: RE: Refrigerator temperature range 2-8 C Date: Fri, 14 Jan 2000 12:47:36 -0800 Bob Davis of UNICEF brought to my attention that some EPI materials and country programs recommend keeping refrigerators at 0-8 degrees C, not 2-8 degrees C. Since hepatitis B vaccine freezes at -0.5 C, and may be introduced in new countries in the coming years, I wonder if Technet members would support a recommendation to WHO and UNICEF that refrigerator temperatures be kept at 2-8 C? Thank you, Mary Mary Catlin Program Officer Program for Appropriate Technology in Health (PATH) 4 Nickerson Street Seattle, WA 98109-1699 USA Tel: (206)285-3500 Fax: (206-285-6619) E-mail:[email protected] ____________________________________*______________________________________ 3. VACCINE FREEZING AND FROST FREE REFRIGERATORS, CONTINUED In Post0212, VACCINES & COLD CHAIN, 26 November 1999 Anthony Battersby, FBA, raised the issue of the risk of vaccine freezing in 'Frost Free' refrigerators which have sub-zero temperatures in some parts of the refrigerator cabinet. The discussion continued in Post0214, VACCINE FREEZING,on 07 January 2000. Hepatitis-B vaccine has a melting point of -0.5'C, while other freeze sensitive vaccines freeze between 0'C and -4'C. See posts 3 and 4 in this TECHNET Forum posting for other related issues. Action, comments and additions please: [[email protected]][email protected][/email] or use your reply button ___________________________________________________________________________ Date: Fri, 7 Jan 2000 08:52:33 -0800 From: [[email protected]][email protected][/email] (Mikko Lainejoki) Subject: Frost free refrigerators To: [[email protected]][email protected][/email], [[email protected]][email protected][/email] Anthony, Allan, I have spent this week reading through old messages and found Anthony's message on frost free refrigerators. In my opinion the message is quite an over-exaggeration and may do more harm than good. Even if we wanted we cannot construct a refrigerator described by Anthony (ref. fundamentals of thermodynamics and heat transfer): Quote The problem is that at the point of entry into the refrigerator cabinet this air is at -15/-20degC. The result is that the middle part of the refrigerator may be as cold as -7DegC while the rest is at +4DegC. Unquote I'm sorry to miss the Harare meeting; hope everything went well. Best wishes for the New Year. mikko --- Date: Fri, 7 Jan 2000 07:06:42 -0500 From: Anthony Battersby Subject: Frost free refrigerators To: Mikko Lainejoki , Cc: Dear Mikko, Multiflow /frost free systems exist it is the system of choice for many North American and Far Eastern manufacturers. I was not exaggerating just reporting facts resulting from a field test carried out on 9 multifow refrigerators over three months. Multiflow is risky for vaccine storage. At Technet, Carib (I think it was), confirmed that he had had experience of multiflow systems freezing vaccine. They are not popular in Europe because they use much more energy, but are popular elsewhere because they never need defrosting. Happy New Year Anthony ____________________________________*______________________________________ 4. SOLUTION SUGGESTION FOR VACCINE FREEZING Carl Erickson, Solar Ice Company, offers this solar solution, applicable in certain situations. Action, comments and additions please: [[email protected]][email protected][/email] or use your reply button ___________________________________________________________________________ From: [[email protected]][email protected][/email] Date: Fri, 7 Jan 2000 13:00:00 EST Subject: Solution Suggestion for Vaccine Freezing To: [[email protected]][email protected][/email] January 7, 2000 Dear Technet Subscribers: In regards to the problem of vaccine freezing - I suggest keeping vaccine in cold boxes. Since ice at 0C provides the refrigeration, vaccine can not freeze. If not enough ice is available for the cold box and other uses, or if it is costly to make or provide, I suggest using the ISAAC solar icemaker. I am interested in hearing more about where the problem is occurring. Information about the ISAAC can be seen in Post 195, or by contacting me. Sincerely, Carl Erickson Solar Ice Company [email protected] ___________________________________*_________________________