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COVID-19 Vaccine Stockpiling and Its Potential Impact

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The following article is an opinion piece written by Sophie Prosolek. The views and opinions expressed in this article are those of the author and do not necessarily reflect the official position of Technology Networks.

Mass vaccination programs can provide a long-term solution to the problem of infectious disease, both within and between nations. Once a critical mass of any population is vaccinated, the spread of a disease within that population becomes significantly less likely in an effect known as "herd immunity". While herd immunity remains our best defence against COVID-19, vaccine stockpiling by high-income nations does pose a severe threat to global public health, leaving low- and middle- income nations in a dangerous vaccine deficit.

Since the first emergence of SARS-CoV-2, scientists across the globe have recognized the power of herd immunity and the importance of mass vaccination. Vaccine development began swiftly; the US government initiated Operation Warp Speed (a program to accelerate shot development and distribution) in May 2020, and the first human-trial vaccine data was
published that very month. A growing number of  vaccines have been authorized for usage against SARS-CoV-2 worldwide, with the US and Europe predominantly using Moderna's mRNA-1273, Pfizer's BNT162b2, Oxford–AstraZeneca's AZD1222 and Johnson & Johnson/Janssen's Ad26.CoV2.S shots to protect their populations. While different options from the vaccine market are available for different countries, the demand for their usage far outstrips their supply; this has placed pressure on customers (i.e., governments) to purchase quickly from manufacturers’ in a grab-and-dash approach to mass immunization.

What is vaccine stockpiling?

High-income countries (typically North America, Europe and Australasia) have been able to quickly secure the bulk of the global vaccine supply, leaving low- and middle- income nations in a dangerous vaccine deficit, competing for the remaining available doses and often relying on foreign aid. This is known as "vaccine nationalism", and has seen many high-income nations place their own domestic needs before the needs of others; resulting in a global public health climate that has been associated with a
troubling history of colonialism.  

While SARS-CoV-2 is a new challenge for modern medicine, vaccine stockpiling certainly is not.
Mass immunization as it is known today began in the 1940s, when British children were first routinely offered the vaccine for diphtheria. Since mass immunization began, nations have been stockpiling to protect against numerous diseases, providing critical reserves should an outbreak arise. Such is the role of vaccine stockpiling in national public health that the World Health Organisation (WHO) continues to retain smallpox vaccine stockpiles, despite the disease now being eradicated.

COVID-19 Vaccines Global Access (COVAX) initiative, directed by Gavi, the Vaccine Alliance (formerly the Global Alliance for Vaccines and Immunization), the Coalition for Epidemic Preparedness Innovations (CEPI) and the WHO, was created in response to the growing problem of vaccine inequality. The objective of COVAX remains to ensure equitable vaccine access across the developing world, with over 300 million doses having already been shipped to those in need.

While programs such as COVAX remain essential to mitigate the risks of vaccine stockpiling, some resistance still exists to the donation of vaccine aid from high-income nations.
Earlier this year, United Kingdom Tory rebels warned the Prime Minister against the use of national aid funding to supply COVID vaccines overseas,  claiming  that the use of an  already tight aid budget for vaccine deployment would detract support from other areas of need. However, the RAND (Research and Development) Coorporation calculated a clear financial detriment of vaccine stockpiling, with an estimated $25 billion required to supply lower income countries with vaccines, versus a combined loss of approximately $119 billion a year if the poorest countries are denied vaccine supply.

The biological implications of vaccine stockpiling

The lack of available vaccines to low- and middle- income countries has already caused concerns amongst scientists.
Some researchers fear that a lack of vaccine sharing could result in a greater evolutionary potential and a higher likelihood that the virus will mutate. While most chance mutations are relatively harmless, a few critical changes in the virus’ genetic material can have functional effects within SARS-CoV-2 proteins. Some protein-level changes can potentiate greater infectivity, transmissibility and even immune escape. When a virus mutates to become significantly different from its precursor, a new variant has emerged.

Viral sequencing and vaccine deficits

Analyzing the genetic sequence of the virus can help expert scientists identify viral variants, providing indications on their potential threat and informing the pandemic response. For many high-income nations, SARS-CoV-2 sequencing has played a key part in their pandemic response strategy; however, just as low- and middle- income nations have struggled in the face of their vaccine deficit, they too battle a lack of viral sequencing capacity.

Pakistan is just one of the lower-middle-income countries which, despite being support by COVAX, remains at risk of high levels of viral transmission. Lack of  equipment and the expertise required for variant detection sequencing has meant that Pakistan relied on UK-based scientists for support.
Dr. Muhammad Yasir is a Pakistani national working as a postdoctoral researcher and SARS-CoV-2 sequencing scientist at the Quadram Institute in Norwich (UK).

Yasir understands the importance of vaccination in the fight against viral variants, having been one of the first scientists worldwide to explore the COVID-19 variant profile in the bustling Pakistan city of Lahore. “Viral sequencing is vital to making informed decisions about lockdowns and travel advice,” says Yasir. “The risk [of variant emergence in Pakistan] can be quite different compared to developed countries, as the Pakistan social network is quite dense." Yasir’s work will be used to directly inform the vaccination strategy in Pakistan. Without sequencing, the impact of a vaccine deficit on viral evolution would be unknown, reducing vaccination to a stab-in-the-dark approach to public health.

Mathematical modeling and vaccine stockpiling

Mathematical modeling approaches have now been developed in order to study the impact of COVID-19 vaccine stockpiling and to find an optimal distribution of doses.
A recent study conducted jointly between Princeton University (New Jersey, US) and McGill University (Quebec, Canada) explored the effect of different vaccine-sharing schemes on the persistence of SARS-CoV-2 infection. The study used mathematical models to safely demonstrate the impact of different dosing regimes on the number of cases and the emergence of variants, without a real-world risk. Comparing models of low vaccine access with equivalent models of high vaccine access, the scientists demonstrated that stockpiling led to an increased infection rate in regions with fewer doses.

While the study accounted for the emergence of new variants, it was not designed to explore the role of viral sequencing in mitigating the risk of vaccine deficit. However the findings did suggest that, if vaccine sharing was more equitable, the respective national cost of genomic surveillance would be reduced.

COVID-19: Lessons learned

Many global lessons have been learned as a result of the COVID-19 pandemic; not least that while many mass immunization programmes are imperfect, they remain lifesaving public health initiatives. While some may consider it "too late" to reverse the social and economic impacts of SARS-CoV-2, certainly the world is better prepared should a future pandemic ever arise. For the first time since mass immunization began, viral sequencing has enabled genomic surveillance, the detection of variants and contributed to national public health strategies. While vaccine stockpiling may worsen the impact of COVID-19, multifaceted, genome sequencing approaches can help to mitigate at least some of the risk.

About the author

Dr. Sophie Prosolek completed her PhD in the field of Molecular Nutrition before moving on to work as a postdoctoral sequencing scientist specialising in Illumina technology for COVID-19 genomics. Sophie now works as a science communicator for the University of Cambridge COVID-19 Genomics UK consortium, and as a freelance science writer.