Vaccines Are Here. Now What? Part I: Challenges of Distributing Vaccines

Written by: Pei-Hsuan Wu (Molecular Biologist and COVID-19 Action Hub Manager)

In less than a year since the COVID-19 outbreak, dozens of countries (as of 1 February 2021) began to distribute vaccines against the devastating coronavirus. As discussed in our earlier post (2), vaccine development and authorization usually take 10–15 years, so this is an unprecedented feat made possible by a singular focus of the world to end COVID-19. COVID-19 vaccines give us a more positive outlook. The experience has taught us that it is possible to find disease treatments and vaccines when all sectors involved in developing, testing, manufacturing, and approving processes of a vaccine or drug collaborate.

This is not to say that all this good news comes without doubts and controversies. For example, two of the leading vaccines approved for use in many countries, made respectively by Moderna and Pfizer/BioNTech4, are “RNA” vaccines. While RNA vaccines have the advantage of easier and less costly production, RNAs are molecules that quickly become unstable outside ultra-low (–70ºC, Pfizer/BioNTech) or low-temperature (–20ºC, Moderna) freezers3. Consequently, they need cold storage at all times to remain effective, including during transportation, which poses a major challenge in many facilities and countries. In addition to technical difficulties, professionals in fields ranging from medicine to politics face many other unsolved challenges. Some problems are related to the process of vaccine distribution.

Specific challenges concern the logistics of immunizing a world population of 7.5 billion people. In theory, not everyone needs to be vaccinated. Herd immunity” happens when a substantial portion (but not necessarily all) of a population is protected by antibodies that their bodies produce to fight viral infection (5). In this scenario, because the vast majority of people can no longer contract or spread the disease, the likelihood of infection for those who are not vaccinated becomes extremely low. For example, one of the deadliest diseases, polio, has been eliminated in many countries thanks to vaccination (since 1979 in the U.S.), even though dozens to hundreds of polio cases were still reported globally every year in the past 3 years6. Although natural infection of a large portion of the population, in theory, can also achieve herd immunity, it is not only ineffective but also dangerous. The antibody response varies widely from person to person, and the immunity is not guaranteed to last a lifetime5. Furthermore, COVID-19 infection can cause death or long-term health damages.

The portion of the population required to stop an outbreak worldwide depends on the disease. For example, vaccination of >95% of the population achieved herd immunity against measles and >80% of the population to stop transmission of polio (7). The exact portion for reaching herd immunity for COVID-19 is not currently known. However, based on experience learned from other diseases, a sufficiently large immunized population means that at least billions of individuals need to be vaccinated to eliminate COVID-19. A year since the coronavirus outbreak, the world is grappling with 2.2 million lost lives (since 22 January, 20208). Worldwide, tens of thousands of deaths caused by COVID-19 have been reported daily (13,936 on 31 January 2021) (1). With an urgency to end the pandemic but limited vaccines, priority setting has immediate consequences.

Among logistic challenges of vaccinating billions of people is who gets the vaccines first. In countries that have begun to vaccinate their residents, people most likely to contract or suffer from the severe complications of COVID-19 are the first in line to get the vaccines9. These people include older people, people with underlying health conditions, essential workers (including healthcare workers), and those living in high-risk conditions, such as prison inmates10. Some decisions are embraced by nearly all authorities (e.g., healthcare workers), while others face political challenges (e.g., prison inmates) (11).

An equally important question that is not as obvious is who should not get the vaccines. An example attracting increasingly heated discussions is whether pregnant women and breastfeeding mothers should be vaccinated against COVID-19. We will take a look at this topic in the Part II article.

Further Readings

1. Coronavirus (COVID-19) Vaccinations – Statistics and Research. Our World in Data. Retrieved 1 February 2021, from

2. Wu, P.-H. Vaccines and Why We Need Them for Fighting COVID-19: Part III. COVID-19 Action Hub at United People Global. 2020.

3. Why Does Pfizer’s COVID-19 Vaccine Need to Be Kept Colder Than Antarctica?National Public Radio (NPR). 2020.

4. Zimmer, C., Corum, J., & Wee, S. COVID-19 Vaccine Tracker Updates: The Latest. The New York Times. Retrieved 1 February 2021, from

5. Mayo Clinic. Herd Immunity and COVID-19 (Coronavirus): What You Need to Know.” 2020.

6. Polio Elimination in the U.S. 2019. Centers for Disease Control and Prevention.

7. Coronavirus Disease (COVID-19): Herd Immunity, Lockdowns and COVID-19.World Health Organization (WHO). 2020.

8. COVID-19 Map. Johns Hopkins Coronavirus Resource Center. Johns Hopkins University. Retrieved 1 February 2021, from

9. Heath, R., & Paun, C. Governments Around the World Weigh Thorny Question: Who Gets the Vaccine First? POLITICO. 2020.

10. Rabin, R. C. Prisons Are Covid-19 Hotbeds. When Should Inmates Get the Vaccine?The New York Times. 2020.

11. Stanley-Becker, I. Early Vaccination in Prisons, A Public Health Priority, Proves Politically Charged. Washington Post. 2021.


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