Quo Vadis, COVID-19 Vaccine?

We have a vaccine for COVID-19.

Finally this pandemic could be over with. Hurrah!

Late last year, Pfizer, Oxford-AstraZeneca, Sinovac, and other developers announced their successful endeavours in producing effective vaccines against COVID-19. Despite differences in methods and production techniques, all claimed that their vaccine is over 60% effective, qualifying WHO criteria of over 50%.^1,2 Some even claim to be over 90% effective.²

Even as the production of vaccines was being ramped up, the number of people requiring the COVID-19 vaccine outweighed the number of doses available. This limitation poses a key question: ‘who should get vaccinated first?’.

The body responsible for regulating vaccine disposals in the UK, the Joint Committee on Vaccination and Immunisation (JCVI), recommended prioritising elderly first. The reason is simple; elderly, men and women aged more than 59 years, are the most susceptible to the disease.³ This group typically have less fitness and would likely succumb to the severe effects of the disease and death compared to the younger counterpart of the population. The difference is huge: compared to people aged 18-29 years, people aged over 50 are 4-13 times more likely to be hospitalised and 30-630 times more likely to die with COVID-19.⁴

For some, prioritising elderly seems like an obvious choice. If you were given the vaccine, who would you protect; one who is likely to suffer severe symptoms and dies or one who would likely develop minor symptoms and recover on their own? Perhaps simplistically, a dose of vaccine has more life-saving value when given to the elderly.

However, some suggest that it might not be the best way out of this pandemic.

To begin with, one should be aware of the limitations in the trial studies. Overall, people aged >59 years are less likely to be recruited in a vaccine trial study because they may be less fit compared to the younger counterparts of the population. For example, the Oxford-AstraZeneca COVID-19 vaccine trial only included about 12% of those aged over 55.^2,5 Sinovac, in comparison, do not even include people over 59 years at all.³ This inadvertent exclusion means that there are knowledge gaps in the safety and efficacy data for vaccinating the elderly group prioritised above. Isn’t it ironic to start the vaccination in whom safety and efficacy are actually less known?

Justification for vaccinating the younger age group first become apparent when one considers that vaccine is also indirectly protective by means of cutting out transmission. Younger people: working class (24-55 years), students (18-24 years), and school children (5-18 years) are significantly more active and mobile compared to the elderly.⁶ Their interaction and movement drive virus transmission among population and halting it has been the key behind successful lockdown measures.⁶ Hence immunisation in these groups, like lockdown, is meant to cut transmission.

Protecting population by vaccinating them and delivering immunity benefits to not only the recipients, but those around them as well is the basic concept of ‘herd immunity’. For COVID-19, herd immunity is achieved when 70% of the population become immune to the disease and, in this case, might be accelerated by prioritising high-transmission groups.⁶ To illustrate, influenza vaccine given to schoolchildren also prevent influenza and pneumonia in the elderly because the disease is typically highly transmitted among children who eventually transmit the disease to their grandparents.⁷ Influenza vaccination in children therefore, result in elderly protection as well by means of herd immunity.^6,7 Could this also mean that the COVID-19 pandemic could be more effectively controlled if we vaccinate the young first?⁸

This rationale is adopted by Indonesia.^9,10 Faced with a huge gap between vaccine necessity and availability, Indonesian regulators are seeking to capitalise on every single dose of the COVID-19 vaccine.⁹ Regulators believe a dose of vaccine is less effective when given to elderly who are less frequently exposed and less likely to transmit the disease.¹⁰ Therefore, instead of prioritising the elderly, Indonesia is inoculating the younger population. This may sound counterintuitive given the elderly’s significantly higher mortality risk, however, when there is no guarantee of enough doses for direct protection, regulators are counting on vaccine’s indirect protection instead.

Additionally, in developing countries, COVID-19 socio-economic effect could be more catastrophic than the disease itself. Business cessation, job-loss and the connected issues of poverty and starvation threaten millions beyond the high-risk group.⁹ Regulators must therefore direct constructive efforts towards achieving quicker herd immunity, easing of social-distancing measures, return-to-work order and the rebuilding of economy.⁹ There simply is not enough time and resource to vaccinate the high-risk first and prolong the lockdown to halt transmission.⁹

Nevertheless, as much is still unknown about this disease, it would be difficult to conclude the best course of action. Only time will tell. Now, if you were given the vaccine, which direction would you go for; decreasing the high-risk or high-transmission first? Quo vadis?*

*Latin phrase for: Where are you going?

References

1. Zhang Y, Zeng G, Pan H, Li C, Hu Y, Chu K, et al. Safety, tolerability, and immunogenicity of an inactivated SARS-CoV-2 vaccine in healthy adults aged 18–59 years: a randomised, double-blind, placebo-controlled, phase 1/2 clinical trial. Lancet Infect Dis. 2020; Available from: http://dx.doi.org/10.1016/S1473-3099(20)30843-4
2. Voysey M, Clemens SAC, Madhi SA, Weckx LY, Folegatti PM, Aley PK, et al. Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK. Lancet. 2020;99–111.
3. Krelle H, Tallack K. The COVID-19 vaccine: who gets it first?. The Health Foundation. 2021 [cited 16 February 2021]. Available from: https://www.health.org.uk/publications/long-reads/the-covid-19-vaccine-who-gets-it-first#lf-section-110211-anchor
4. Centers for Disease Control and Prevention. Older adults| At greater risk of requiring hospitalization or dying if diagnosed with COVID 19. CDC. 2020. Available from: https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/older-adults.html
5. Ledford H. Oxford COVID-vaccine paper highlights lingering unknowns about results. Nature. 2020; 378-379 (588). Available from: https://doi.org/10.1038/d41586-020-03504-w
6. Davies NG, Klepac P, Liu Y, Prem K, Jit M, Pearson CAB, et al. Age-dependent effects in the transmission and control of COVID-19 epidemics. Nat Med. 2020;26(8):1205–11.
7. Hull HF, McBean AM, Caldwell D, O’Connor H. Assessing Herd Immunity in the Elderly Following the Vaccination of School Children with Live Attenuated Trivalent Influenza Vaccine (LAIV): A County-Level Analysis. Procedia Vaccinol. 2010;2(1):92–100.
8. Giubilini A, Savulescu J, Wilkinson D. COVID-19 vaccine: Vaccinate the young to protect the old? J Law Biosci. 2020;7(1):1–13.
9. Widianto S, Diela T. Indonesia is vaccinating younger people first. Here’s why. World Economic Forum, Reuters. Available from: https://www.weforum.org/agenda/2021/01/indonesia-vaccinating-working-population-before-elderly
10. Aditya A, Ho Y. Younger people get vaccines first in Indonesia’ unusual rollout. Bloomberg. 2020. Available from: https://www.bloomberg.com/news/articles/2020-12-15/younger-people-get-vaccines-first-in-indonesia-s-unusual-rollout