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Pfizer & BioNTECH's 90% Effective COVID-19 Vaccine and Its Complex Distribution Plan
Pfizer & BioNTECH's 90% Effective COVID-19 Vaccine and Its Complex Distribution Plan
Written By: Paphapin Pairojtanachai
The race to develop a vaccine for the coronavirus has been going on for months, and on Monday, November 9, 2020, global pharmaceutical company Pfizer and its German BioNTech partner company finally announced that an interim analysis of an ongoing Phase III clinical trial has revealed that its vaccine candidate was over 90% effective in preventing symptomatic cases of COVID-19. The vaccine, named BNT162b2, is mRNA-based, and the viral mRNA that it contains codes for the surface protein of the SARS-CoV-2, which allows the virus to attach to and enter human cells. The BioNTech team designed the vaccine using the mRNA strand that was most likely to be delivered to dendritic cells, which create replicas of the “spikes” of the coronavirus and “present” them to the immune system to recognize them, initiate responses, and build a memory of the virus.
The Phase III study for this BNT162b2 vaccine candidate has involved 43,538 volunteers who had no evidence of being infected with the coronavirus prior to the clinical trial. The vaccination includes two doses, injected three weeks apart. Seven days after the participants have received the second dose (or 28 days after the initiation of the vaccination), the Data Monitoring Committee reported that “among people who received the vaccine, there were more than 90 percent fewer symptomatic cases of COVID-19 than among people given a placebo.” At the time of analysis, the COVID-19 case count within the study has reached 94 cases, but the two companies stated that they will continue the trial and collect further data for a final analysis when there have been a total of 164 confirmed COVID-19 cases. The final vaccine efficacy percentage may change by that time, but the companies hope to apply for an emergency use authorization of the vaccine by the US Food and Drug Administration (FDA) by the third week of November, which is when they will have accumulated at least two months of safety data following the final dose of vaccination. The trial participants will also be monitored for an additional two years after they have received the second dose.
Considering that the FDA guidelines recommend that COVID-19 vaccine efficacy percentages are at least 50% — in other words, the vaccines should reduce the number of coronavirus cases by half when compared to a placebo — the BNT162b2 vaccine candidate has exceeded that benchmark by a long way. However, this is concluded based on preliminary analysis, and since the study is still continuing, it cannot be said for certain that the vaccine’s 90% effectiveness will be maintained over time. Even so, this is a sign of encouragement for the success of other mRNA vaccine candidates, such as one being developed by Moderna, as well.
Despite the excitement of this news, many unanswered questions and challenges still remain, one of which is how the vaccine will be delivered to billions of people across the world. In order to preserve the genetic material, the BNT162b2 vaccine has to be stored under ultra-cold temperatures ranging from minus 90 to minus 60 degrees Celsius; this is 20 degrees lower than the coldest temperature requirement for a vaccine currently being used in the United States. The solution to this problem requires large amounts of dry ice, which is currently scarce in many parts of the country, and most hospitals, pharmacies, and laboratories do not have freezers that are able to reach such ultra-low temperature.
As of now, it seems like Pfizer has devised a “thermal shipper”, which is a box that is designed to store the vaccine along with dry ice. Upon receiving the thermal shippers filled with vaccines, clinical sites are supposed to refill the box with dry ice within 24 hours and every five days afterwards if the vaccines are not used by that time. In addition, the box can be opened for no longer than a minute, and only two times per day. Once taken out of the box, the vaccines will last for five days in the refrigerator, and the doses have to be injected within six hours after they have been thawed and diluted.
This process is very specific and unconventional, and it is not entirely clear that the thermal shippers will work efficiently. Moreover, handling dry ice can be hazardous to healthcare workers. Hence, even if the FDA approves this BNT162b2 vaccine candidate for emergency use authorization, the issue of its distribution plan still has to be dealt with.
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