POST 00511E : USE OF VVMs
Anil Varshney (mailto:
[log in to unmask]) from India has observations
and questions on VVM use, to which Ümit Kartoglu (mailto:
[log in to unmask])
from WHO provides answers.
_____________________________________________________
I wish to present some observations which need to be cleared
In East Timor, CCM, VVM and Freeze Watch are in use in the cold chain,
which is LPG-run SIBIR refrigerator with front door opening.
The following points were noticed :
1. VVM on OPV and BCG showed different stages even when kept for the same
duration at the facility while the VVM in OPV was in stage 2-3 the CCM
marker showed that the vaccine could be used for 2 months.
2. Freeze Watch was a good indicator, but its interpretation from central
to peripheral level was poor – showing there is need to increase the
awareness through training and other methods.
Questions raised
1.Why different VVM stages in BCG and OPV , do both VVM have different
characteristics?
2. In most cases the VVM on OPV appeared to show that the cold chain is
inadequate while CCM cards allowed for more relaxation. If VVM is more
sensitive than its better NOT to use the CCM card as the health worker is
likely to get confused..
3. If the cold chain is not adequate for OPV, it does not necessarily mean
that it is not OK for other vaccines.
4. Since OPV is coming with VVMs, the CCM card should mention other
vaccines only (without OPV) in order to avoid confusion in the peripheral
health facilities.
__________________________________________________________
Anil's contribution and questions he raised show the importance of having a
good reference material on Vaccine Vial Monitors (VVM).
I would like to announce that the following document will be made available
soon (within a month or so) both in electronic and hard copy: "Getting
started with vaccine vial monitors: Questions and answers on field
operations". This document will replace the old "Vaccine Vial Monitor and
open vial policy - questions and answers WHO/EPI/LHIS/96.01"
Post 00444E (3 April 2002) was sent with an attachment: "Specifications for
Vaccine Vial Monitors (E6/IN5, 25 March 2002)". It is thus highly
recommended that readers revisit this posting and the attachment through
TechNet21 archives at:
http://listes.ulaval.ca/cgibin/wa?A2=ind0204&L=technet21e&F=&S=&P=274
Coming back to Anil's questions:
1. Why different VVM stages in BCG and OPV , do both VVM have different
characteristics?
Yes. VVMs are manufactured with four specific time-temperature
sensitivities. They are the following:
VVM type 37oC 25oC 5oC
VVM30 30days 193days >4years
VVM14 14days 90days >3years
VVM7 7days 45days >2years
VVM2 2days NA 225 days
Each type of VVM is designed to mimic the heat stability of the vaccine to
which it is attached. Types of VVMs are assigned by WHO based on the heat
stability data of that particular vaccine provided by the vaccine
manufacturer. VVM for OPV and BCG are of different types and should behave
differently. BCG is a more heat-stable vaccine compared to OPV, and if both
vaccines with VVMs attached are kept at the same temperature, OPV VVM will
reach its discard point much before BCG VVM.
Unfortunately it is NOT possible to provide a list that shows VVM type by
vaccines. For each presentation, WHO reviews the heat stability data and
assigns an appropriate category for that particular one. For example, BCG
from one manufacturer can take VVM14 while another one may receive VVM30.
However, we know that all OPV is VVM2.
2. In most cases the VVM on OPV appeared to show that the cold chain is
inadequate while CCM cards allowed for more relaxation if VVM is more
sensitive than its better NOT to use the CCM card as the health worker is
likely to get confused.
We have to make a clear distinction between the purpose of the Vaccine Cold
Chain Monitor (CCM) and VVM. CCM cards, packaged with each consignment of
vaccine from UNICEF, indicate when the temperature limits of the cold chain
have been passed. The VVM takes the monitoring procedure one step further
and shows the impact of any such temperature changes on each individual
vial of vaccine. The CCM monitors the journey while the VVM shows how "each
passenger" has fared.
The CCM is a useful managerial tool for checking the arrival of vaccine
shipments at primary and intermediate stores and may also be used in
conducting national cold chain surveys. The VVM provides guidance on the
use of each vial of vaccine.
In the presence of both VVM and CCM, VVM reading should have the priority.
One should keep in mind that VVM is the only time-temperature indicator
that accompanies the individual vial starting from the primary packaging of
the vaccine at the manufacturer's facility until the time it is used in the
field. This is not possible with CCM. It is also highly possible that a CCM
activated at any point of the cold chain will not have the historical
information of heat exposure of the vaccines present in the cold chain at
that point in time. Therefore, it is very difficult to make a correct
interpretation of a CCM reading for making managerial decisions at
different levels of the cold chain system.
3. If Cold chain is not adequate for OPV it does not necessarily mean that
it is not OK for other vaccines?
Different vaccines require different temperature ranges for transportation
and storage. WHO recommends that OPV be kept at -15° to -25°C at primary
and regional intermediate vaccine cold stores. Rest of the vaccines can be
safely kept at +2° to +8°C at all levels. WHO no longer recommends that
freeze-dried vaccines be stored at -20°C. Storing them at -20°C is not
harmful but it is unnecessary. Instead, these vaccines should be kept in
refrigerators and transported at +2° to +8°C.
4. Since OPV is coming with VVM, the CCM card should mention other vaccines
only ( without OPV) in order to avoid confusion in the peripheral health
facilities.
As mentioned under 2nd answer, CCM is mainly designed for checking the
arrival of vaccine shipments. WHO requires that one CCM card is inserted
into each vaccine shipping box. For example, a shipment of 1,000,000 doses
of 10 dose/vial DTP vaccine will come around 50 shipping boxes with a CCM
card in each. If the same box is transferred to a lower level (intermediate
vaccine store), it can definitely go with the original CCM card. However,
it is very unlikely that any country can have enough CCMs to accompany
distribution of vaccines down to service level. Activating new CCM card is
NOT a solution and is NOT recommended since it will give misleading information.
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