Since December 2021, when several novel unprecedented vaccines against SARS-CoV-2 began to be approved for emergency use, there has been a worldwide effort to get these vaccines into the arms of as many people as possible as fast as possible. These vaccines have been developed “at warp speed,” given the urgency of the situation with the COVID-19 pandemic. Most governments have embraced the notion that these vaccines are the only path towards resolution of this pandemic, which is crippling the economies of many countries.
Thus far, there are four different vaccines that have been approved for emergency use for protection against COVID-19 in the US and/or Europe. Two (the Moderna vaccine and the Pfizer/BioNTech vaccine) are based on mRNA technology, whereas the other two (produced by Johnson & Johnson and AstraZeneca) are based on a double-stranded DNA recombinant viral vector. The mRNA vaccines contain only the code for the SARS-CoV-2 envelope spike protein, whereas the DNA-based vaccines both contain an adenovirus viral vector that has been augmented with DNA that codes for the SARS-CoV-2 spike protein.
The DNA-based vaccines have a certain advantage over the RNA-based vaccines in that they do not have to be stored at deep-freeze temperatures, because double-stranded DNA is much more stable than single-stranded RNA. But a disadvantage is that those who have been exposed to natural forms of the adenovirus have antibodies to the virus that will likely block the synthesis of the spike protein, and therefore not afford protection against SARS-CoV-2.
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