Covid-19 vaccines

The most promising tools in controlling the Covid-19 pandemic are the new vaccines which several drug companies have developed.
As of this writing, two vaccines have already been approved for full use and five vaccines are in early or limited use. Forty-two vaccines are in phase one trials, 16 in phase two, and 17 in phase 3 trials.
A messenger RNA vaccine was initially developed by BioNTech in January 2020 then partnered with New York-based Pfizer in March. Clinical trials started in May 2020.
Results showed the vaccine has 95 percent efficacy in preventing laboratory-confirmed symptomatic Covid-19 patient. The Pfizer-BioNTech vaccine was approved for use in Canada and other countries and on Dec. 11, the U.S. Food and Drug Authority authorized the Pfizer vaccine for emergency use. The companies aim to produce 1.3 billion doses by the end of 2021.
The vaccine is given in two doses, three weeks apart through muscle injection. Storage is by freezer only at a temperature of -70 degrees Celsius.
Development of the vaccine was started by BioNTech in January 2020. It used messenger RNA of the SARS-CoV2 virus to encode for spike proteins of the virus and when injected the vaccine provokes the immune system to produce antibodies against spike proteins of the coronavirus. It was also shown that aside from antibodies, there are other immune system cells – called T-cells that are formed. Protection was noted less than two weeks after the first dose, boosted by the second dose after three weeks. It showed similar protection among different races – black, white and Latino volunteers and among patients with conditions like diabetes mellitus and obesity. Same efficacy was noted among elderlies compared to those less than 65 years old.
The MRNA vaccine created by Boston-based company Moderna has shown 94 percent efficacy. It is under U.S.FDA review and if authorized for emergency use, the first injections would be given on Dec. 21.
Adenovirus vaccines include those developed by CanSino which is on limited use in China, by Gamaleya which is in early use in Russia, and by Johnson & Johnson now in phase three trials, and Oxford-Astra Zeneca.
Viral protein vaccines were also made by Novavax and by Vector Institute, and the latter is now in early use in Russia. Vaccines using inactivated virus were developed by Chinese state-owned company Sinopharm, now approved for use in the United Arab Emirates and Bahrain and of limited use in China.
One vaccine is an adenovirus vector vaccine with 70 percent efficacy using full-dose in the initial cases studied, but higher efficacy rate was seen among patients inadvertently given half-the intended dose.
In early clinical trials on humans, it has been shown that protective antibodies and immunogenicity developed without major side effects.
The Pfizer-BioNTech vaccines have caused fatigue, fever, and muscle pains in some cases. Allergic reactions have also been reported.