 With roughly 71 million COVID-19 vaccine doses administered worldwide, 24.5 million doses given in the United States alone, humanity is experiencing one of the largest-scale global health efforts in history. There are dozens of different COVID-19 vaccines in various stages of development throughout the world that have the potential to be approved. As of writing this article, the World Health Organization (WHO) has identified 63 vaccine candidates in the clinical phase. Currently, the vaccines authorized for emergency use in the United States are the Pfizer-BioNTech and Moderna mRNA vaccines. These vaccines are a great first step into widespread vaccination, but there are several barriers limiting their use.
One of the biggest challenges for mRNA vaccines is their extremely strict storage requirements for stability, which are not unique to the Pfizer or Moderna formulations. The Pfizer vaccine is supplied as a frozen, 5-dose vial that is stored between -80ºC to -60ºC and has to be thawed and diluted prior to administration. After dilution, they have to be stored between 2ºC to 25ºC and used or discarded within 6 hours from the time of dilution. The Moderna vaccine also comes in multi-dose vials but has slightly less strict temperature requirements. They are stored frozen between -25ºC to -15ºC, but can be stored refrigerated between 2ºC to 8ºC up to 30 days prior to first use. Another limitation is that the Pfizer vaccine is recommended for people aged 16 years and older, while the Moderna vaccine is approved for people aged 18 years and older. If these mRNA vaccines have so many drawbacks, what other options will there be in the future? Despite the fact that the only COVID-19 vaccines currently available are mRNA vaccines, this vaccine type is actually relatively new and uncommon. To date, there are no other approved mRNA vaccines on the market. According to the WHO’s novel coronavirus vaccine landscape, only 7 of the 63 vaccines in development are RNA based. An additional 9 vaccines under development are DNA-based. In contrast, there are 20 protein subunit vaccines in clinical development. Another 16 vaccines in the viral vector class as either replicating or non-replicating varieties with or without additional antigen presenting cells are also identified. In the whole virus vaccine category, there are 9 inactivated virus vaccines and 1 live attenuated vaccine. The latest vaccine that has been approved in the UK is a viral vector vaccine developed by AstraZeneca and the University of Oxford. The vaccine has a reported efficacy of 90% and is stable for refrigeration. Their clinical trials, which involved over 11,000 people, found the vaccine’s 90% efficacy figure in those that received a low dose followed by a standard dose. Surprisingly, in participants that received two standard doses the efficacy of the vaccine was only 62.1%. One of the major benefits of the vaccine is its price of $4 per dose, much lower than the $20 of the other available vaccines. However, there have been problems with supply and pricing. The UK has ordered 100 million doses, Australia has ordered 53 million, and the EU has a contract with AstraZeneca to provide up to 400 million doses in total, around 80 million of which were due this quarter. Unfortunately, AstraZeneca reported on January 22 that they will only be able to deliver 31 million doses to the EU and supply chain issues likely affect their other agreements as well. The U.S. still has not approved the vaccine due to delays in clinical trials. Some other major viral vector vaccines production includes Jannsen/Johnson&Johnson’s vaccine, which also has an agreement for 400 million doses with the EU once its year-long clinical trial is finished. They launched their phase 3 trials in Latin America and the UK in fall of 2020. The Ganekaya Research institute in Russia is also developing a viral vector, called Sputnik V, that has just entered phase 3 trials. It has a reported effectiveness of 92% and can be stored at normal fridge temperatures. Another U.S. based biotech company, Novavax, has recently finalized an agreement with Canada to purchase 52 million doses and concluded talks with the EU for up to 200 million doses for their fridge-stable protein subunit vaccine. The French company Sanofi and England-based GSK also have a protein subunit vaccine that is stable at refrigerator temperatures and can even be stored at room temperature for a short amount of time. The EU has already confirmed the purchase of 300 million doses of their vaccine. Additionally, Sanofi has just finished settling an agreement to assist in producing 100 million doses of the Pfizer/BioNTech vaccine just hours before writing this article. Information on vaccines in development in China is more difficult to obtain, but Sinovac’s inactivated vaccine is currently approved for emergency use in China. The country currently has the second highest number of vaccines given in the world at 15 million in total. Other countries have already reached agreements with Sinovac, such as Turkey approving 10 million doses of the vaccine. The latest figures of its effectiveness put it at around 50.4%, making it an unlikely contender at its reportedly $60/dose price tag. Sinopharm, which is a state-run company, is also developing two inactivated vaccines of its own. Reports of its efficacy are a little inconsistent but hover around 80% effectiveness. Regardless, the United Arab Emirates has already approved the Sinopharm vaccine earlier this month. The vaccines mentioned in this article are nowhere near an exhaustive list of all the potential vaccines that may come out to protect against COVID-19, which is great news. As the effort to push for global immunity to the virus that turned the world on its head continues, it’s reassuring to know that several different options will eventually become available for the public in the coming years. More than likely, a set of gold-standard vaccines will be developed in the years to come that will join the likes of influenza on the list of regularly scheduled vaccinations. Written by: Kervin Novido References: ● https://www.gavi.org/vaccineswork/covid-19-vaccine-race ● https://www.gavi.org/vaccineswork/there-are-four-types-covid-19-vaccines-heres-how-they-work ● https://www.who.int/publications/m/item/draft-landscape-of-covid-19-candidate-vaccines ● https://www.bloomberg.com/graphics/covid-vaccine-tracker-global-distribution/ ● https://www.fda.gov/media/144245/download ● https://www.fda.gov/media/144637/download ● https://www.novavax.com/covid-19-coronavirus-vaccine-candidate-updates ● https://clinicaltrials.gov/ProvidedDocs/60/NCT03681860/Prot_SAP_000.pdf ● https://ourworldindata.org/covid-vaccinations ● https://pubmed.ncbi.nlm.nih.gov/33306989/ ● https://fortune.com/2021/01/25/astrazeneca-covid-vaccines-europe-deliveries-south-africa-price/ ● https://www.news.com.au/world/coronavirus/australia/doctors-in-australia-will-bulk-bill-covid19-vaccinations-making-it-free-for-members-of-the-community/news-story/1e7beed205791af4fd60f45cfc56fe93 ● https://www.bbc.com/news/world-europe-55822602 ● https://www.bbc.com/news/world-asia-china-55212787 ● https://www.fiercepharma.com/pharma/despite-pfizer-s-high-efficacy-expectations-other-covid-vaccines-may-have-a-logistics-edge#:~:text=Pfizer's%20vaccine%20must%20be%20kept,35.6%20and%2046.4%20degrees%20Fahrenheit. ● https://www.cnn.com/2021/01/27/europe/sanofi-vaccine-doses-intl/index.html
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