To get the COVID-19 vaccine approved quickly, companies focused on proving the efficacy. They did not run trials to find the optimal dosage or storage to maximize public health. For example, delaying the second dose, fractional dosing, removing freezer temperature requirements are all ways of increasing the distribution and reaching herd immunity faster.
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A mutation of COVID-19 is spreading quickly throughout the world and threatens recovery efforts. The Alpha variant is believed to be 50% more transmissible than other local COVID-19 types. The Delta variant is 60% more transmissible than the Alpha variant.
According to a recent study, people over the age of 80 that were given the second dose of the Pfizer COVID-19 vaccine 12 weeks after the first dose ended up with over three times as many antibodies after the second dose. While this study was only for the Pfizer vaccine it could significantly change the vaccination strategy of many countries.