Küresel COVID-19 aşılarının önde gelen üreticileri ortaya çıktı ve ilk enjeksiyonlar İngiltere, Amerika
Birleşik Devletleri ve başka yerlerde uygulanmaya başlandı. Ancak bu çok beklenen aşıları dünya çapında
dağıtmanın yolu, derin dondurmalar, dikkatli zamanlama, uçaklar, trenler, kamyonlar derken, beklenenden
zorlu geçecek.
Aşağıda, son aşama denemelerinde yeni koronavirüs enfeksiyonlarının önlenmesinde etkili olan, önde gelen
üç deneysel aşının yolculuklarına göz atacağız. İlki Pfizer Inc ve BioNTech SE’den, ikincisi Moderna Inc’den -ABD Ulusal Alerji ve Bulaşıcı Hastalıklar Enstitüsü ile birlikte ve üçüncüsü AstraZeneca ve Oxford Üniversitesi’nden.
Planes, trains and trucks
Typically, airlines use containers with cooling materials, such as dry ice, to transport pharmaceutical
products, but some don’t have temperature controls, making products susceptible to unforeseen events
such as flight delays.
Airlines are now considering options ranging from a large plug-in freezer, which can cost about as much
as a small car, to a multi-layered canister that uses liquid nitrogen to ship vaccines requiring a deep
freeze.
Some trucks will be packed with dry ice and others will be refrigerated. Some will have no temperature
controls and will rely solely on the cooling stability of the vaccine transport coolers.
Unlike Pfizer’s vaccine which needs to be shipped and stored at -70 Celsius
(-94 F), the Moderna and AstraZeneca
vaccines do not require specialized ultra-cold freezers or vast quantities of dry ice, making it easier
to supply rural and remote areas. UNICEF is working with manufacturers and other partners to procure
COVID-19 vaccines for poorer countries, as well as help them with freight, logistics and storage.
The U.N. children’s agency, which has experience delivering medicines to all corners of the world, calls
the “cold chain” a complex undertaking that requires precise coordination in temperature-controlled
environments to prevent a vaccine from losing its potency. “From storage facilities down to the village
level, health workers carry vaccines in cold boxes and vaccine carriers, traveling by car, motorcycle,
bicycle, donkey, camel or on foot to immunize every last child, even in the most remote of villages,”,
UNICEF said on its website.
Awaiting vaccination
As vaccines travel from the manufacturer to the clinics, shipments will cross time zones and different
environments. But the integrity of the vaccine relies on stable, consistent temperatures.
If the correct cold chain temperatures are maintained, all three vaccines will have a shelf life of about
six months. But vaccines are sensitive to temperature variations and once stability is compromised, it
cannot be recovered. Temperatures should be monitored throughout the vaccine’s shelf life.
Vaccines can be removed from their long-term, temperature-controlled environments anytime before the
six-month expiry date. But once refrigerated or in room temperature, the time of stability becomes
shorter.
Into the arms of the people
Once out of storage, the coronavirus vaccines all have different requirements for prepping. The AstraZeneca vaccine can be administered straight from the vial. The Moderna dose needs a gentle swirl after the vial is thawed. And the Pfizer vaccine, fresh out of a deep freeze, will require dilution and repeated
inversion, but do not shake.
The attention and consideration necessary for the Pfizer vaccine could require specialist skills that may
not be available in all corners of the globe. Timings and protocol will need to be followed closely.
Generally, a vaccine’s real-world effectiveness tends to be slightly lower than its efficacy in clinical
trials.
In the real world, there are multiple, unpredictable factors, including how many, or few, people adhere
to the optimum dosing schedule and timetable; how individuals’ immune systems respond; whether the
vaccine was stored at the correct temperature; whether people know, or don’t know, if they have been
exposed before.
It is also not known how long a vaccine will protect someone from the SARS-CoV-2 coronavirus. BioNTech
Chief Executive Officer Ugur Sahin has said he is optimistic the immunization effect of the vaccine
would last for a year.Experts say that it is likely we will have to live alongside the virus.
The evidence suggests that the COVID-19 vaccines developed by Pfizer-BioNtech, Moderna and AstraZeneca will help stop people developing the disease. Only
AstraZeneca’s data, so far, shows signs that its vaccine may also help prevent transmission of the
virus.
