What’s Happening with the AstraZeneca Vaccine?

AstraZeneca’s seemingly bright future comes to an abrupt halt after recent reports of blood clots in those who have received the jab.

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By Christina Jiang

As we pass the one-year anniversary of quarantine, the single-stranded RNA coronavirus has already taken over 3 million lives and left communities and economies worldwide in shambles. As countries scrambled to formulate vaccines, pharmaceutical companies faced the challenge of creating an affordable, effective, and profitable vaccine for the public. The Pfizer and the Moderna vaccines satisfy the last two conditions, each showing over a 90 percent decreased risk, or efficacy rate, of getting symptomatic COVID-19 in clinical trials. However, their costs range from $15 to $20 per dose. The alternative to this seemed to be Oxford’s AstraZeneca vaccine, which only costs $4 per dose while offering similar efficacy. While its bargain price brought the possibility of a “universal vaccine” for COVID-19, the AstraZeneca vaccine has recently been restricted and even suspended in many countries due to concerns about recent reports of blood clots in those who have taken it.

Vaccines help our bodies build an immunity to a target virus and reduce the severity of a potential infection. To combat a virus like COVID-19, vaccines using mRNA became the front runners in the vaccine race because of mRNA’s ability to be quickly synthesized once a target viral sequence is identified. The mRNA works to instruct the cell to produce just a portion of a viral protein, known as the spike protein, which is unique to COVID-19 and enables the virus to enter host cells and cause infection. Once the mRNA enters cells, the spike proteins appear on the cell surface and trigger an immune response, producing antibodies to fight this induced infection. The immune system remembers parts of the spike protein and produces the same specific antibodies against COVID-19. Like the Pfizer and Moderna vaccines, the AstraZeneca vaccine also provides instructions for cells to express the COVID spike protein, but uses double-stranded DNA rather than single-stranded RNA.

AstraZeneca’s vaccine delivers this double-stranded DNA payload through a viral vector, using a harmless virus to enter and deliver genetic code to our cells. This specific vaccine uses ChAdOx1, a modified chimpanzee virus capable of entering but not replicating in human cells, to deliver the spike protein code to our cells. Because this vaccine uses DNA protected by the protein coat of the viral vector, it is much less fragile than mRNA, allowing it to be refrigerated, rather than frozen, for up to six months. This accessibility separates the AstraZeneca vaccine from its mRNA counterparts, as it does not require expensive freezing storage systems, allowing it to be remarkably cheaper than its competitors.

Almost as if it were too good to be true, the AstraZeneca vaccine has its share of problems. European countries began to approve AstraZeneca in late December. Initial concerns with AstraZeneca’s effectiveness for adults above the age of 65 and its limited supply made countries hesitant to use it, and some temporarily suspended the administration of the vaccine. However, by mid-March, AstraZeneca vaccine rollout resumed in 70 countries.

This progress was short-lived, though, as a report released by the National Institute of Allergy and Infectious Disease (NIAID) on March 23 warned that AstraZeneca possibly used outdated clinical trial data to determine its efficacy. AstraZeneca responded by releasing updated data from their U.S. clinical trials, revealing a 76 percent efficacy rate, rather than the 79 percent efficacy rate they had stated previously. Believing that AstraZeneca was being intransparent, many countries, including the U.S., began to distrust the vaccine. Furthermore, reports by regulators on April 1st describe possible lethal side effects, as 30 people who received the vaccine suffered from mysterious blood clots and concerningly low levels of platelets, with seven cases resulting in death.

In response, some regions have begun to restrict administering the AstraZeneca vaccine, fearing the possible link between the jab and blood clots. After reporting about one case per 100,000 AstraZeneca vaccine vaccinations, Germany stopped giving out the vaccine to adults under 60, despite 2.7 million people having already received the first dose. The Netherlands’ government, which has already given out around 400,000 doses of the vaccine to its citizens, released a statement stating that they will suspend the vaccine usage for people under the age of 60 due to similar concerns.

In the U.S., the AstraZeneca vaccine has not been approved by the Food and Drug Administration. However, director of the NIAID Anthony Fauci has expressed that the US may not even need it since they already have contracts with other leading vaccine companies such as Pfizer. Canada has not received any reports of blood clots, with their chief medical advisor Dr. Supriya Sharma stating that the benefits outweigh the risks. However, Canada ultimately suspended the administration of the vaccine to adults under 55, following a dozen European and Asian countries that have halted the vaccine’s administration, until its safety is confirmed.

Despite the current restrictions, AstraZeneca’s vaccine is still promising. The suspensions are only temporary, depending on when or if AstraZeneca can guarantee its safety. Unless another cheap vaccine like AstraZeneca’s is produced, countries will most likely continue to use AstraZeneca’s more expensive counterparts. While this may not impact the U.S., the sudden rollback of AstraZeneca’s vaccine is an abrupt setback for countries relying on it to provide immunity for those who cannot afford costlier alternatives. With AstraZeneca’s vaccine off the table for now, it is even more important for countries to come together and formulate a vaccine rollout for their people.