How are vaccines made, what made COVID-19 vaccines possible so quickly, and how likely is another pandemic?

How Vaccines Work and Protect Against Disease

A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. Vaccines work by training your immune system to recognize an infectious agent using harmless parts like recombinant protein, genetic material, or weakened forms of germs, giving your immune system a "preview" of the threat so it knows how to respond if it encounters the real thing.

When a vaccine is introduced, it triggers two key responses: antibody production, where specialized proteins called antibodies recognize and destroy the introduced substance, and memory cell formation, which keeps a record of the antigen and allows your immune system to respond more quickly if exposed to the actual pathogen in the future. This training process builds what's known as immunity—a powerful defense that helps your body respond faster and more effectively in the future.

Vaccine Development Timeline and Typical Costs

Vaccine development typically takes about 10-15 years, costs hundreds of millions of dollars to develop a vaccine, and only about one in 15 vaccines that are entering Phase II trials ever becomes licensed. For most diseases, developing a vaccine can take more than 10 years because the development process is expensive, so to keep costs down development takes place slowly, with each stage only beginning when the previous stage is successfully completed.

What Made COVID-19 Vaccines Possible So Quickly

The extraordinary speed of COVID-19 vaccine development—from identification of the virus's genetic sequence to the first doses being administered to the general public in less than 11 months—is due to several factors. The key reasons include:

• The ability to apply the extensive vaccine-development experience of industry and academia, as vaccine development expertise had been developing and licensing vaccines for many decades.
• The COVID-19 genome (genetic code) was mapped within 2 weeks, which helped labs work quickly to target exactly what kind of vaccine could attack the virus.
• Normally, a lot of time is spent waiting for people to become infected to test a vaccine and for regulators to approve things, but the pandemic demanded unprecedented international attention, cooperation and use of resources, enabling rapid action.
• Years were removed from the timeline by cutting out long stretches of waiting built into most human testing, and nearly half a million people in America alone offered themselves for vaccine testing through the COVID-19 Prevention Network in a matter of months.
• Some pharmaceutical companies, bolstered by big vaccine contracts and research cash from the U.S. government's Operation Warp Speed, were churning out doses during clinical trials in hopes that the vaccines would work, and once they had emergency use authorization, they were ready to ship doses immediately.

mRNA Vaccine Technology and How It Differs from Traditional Vaccines

mRNA vaccines work by giving your body instructions to make a small part of the virus so your immune system can generate tools to fight an infection if it sees the virus again in the future. By injecting cells with a synthetic mRNA that encodes a viral spike protein, an mRNA vaccine can direct human cells to make a viral spike protein and evoke an immune response without a person ever having been exposed to the viral material.

When used in vaccines, mRNA delivers the instructions for making a harmless piece of protein identical to one found in a particular virus or bacterium to the 'protein factories' of our cells, and once the instructions have been decoded and the protein assembled, the immune system recognizes it as a foreign body and starts to produce antibodies that can attack the protein if it encounters it again in the form of the 'real' virus.

Researchers have been studying this method of creating vaccines for decades, though most traditional vaccines require loads and loads of virus to first be produced, but mRNA vaccines and other new vaccine technologies don't rely on virus produced in labs—these new classes of vaccines rely on material that can be synthesized in a laboratory. This makes them very quick to develop.

Understanding R0 (Basic Reproduction Number)

The basic reproduction number of a contagious disease, known as R0, is the number of people per infected individual that will be generated throughout its infectious period in a susceptible population. The higher the value of R0, the higher the risk of an epidemic or a pandemic since each individual can potentially infect a larger number of people with the risk of exponential growth.

R0 Values Across Diseases

The R0 value of the 1918 flu pandemic was estimated to be between 1.4 and 2.8, and for an extremely contagious disease such as measles, R0 is thought to lie between 12 and 18. Influenza in its regular form is highly contagious with an R0 between 2 and 4 but has low lethality, while Ebola has a lower contagion with an R0 between 1.5 and 2.5 but is much more lethal.

The R0 for COVID-19 is a median of 5.7, meaning that one person with COVID-19 can potentially transmit the coronavirus to 5 to 6 people, rather than the 2 to 3 researchers originally thought. This higher transmissibility helps explain why COVID-19 spread so rapidly across the world.

Key Vaccine Manufacturers and Technologies

Pfizer is one of the largest pharmaceutical companies globally and has developed several vaccines, including those for COVID-19 such as the Pfizer-BioNTech COVID-19 vaccine, with advancements in vaccine technology, particularly its mRNA vaccine platform, that have revolutionized vaccine development. Moderna is a biotechnology company known for its mRNA vaccine technology, and its COVID-19 vaccine was one of the first authorized for emergency use, with its success opening new avenues for vaccine development against various diseases.

Johnson & Johnson's COVID-19 vaccine, which requires only one dose, has contributed significantly to global vaccination efforts, with its viral vector technology adding diversity to vaccine platforms available in the market. AstraZeneca is a global pharmaceutical company that developed a COVID-19 vaccine in collaboration with the University of Oxford, and has been crucial for global vaccine equity due to its affordability and ease of distribution, with its partnership model facilitating technology transfer and production scale-up in various regions.

Sanofi is the world's biggest manufacturer of flu vaccines, producing vaccines that target meningitis and children's polio. Serum Institute of India is the world's largest producer of vaccines by number of doses, producing 1.3 billion doses a year; its products are used in more than 140 countries.

COVID-19 vs. Ebola: Key Differences

While COVID-19 is highly transmissible, Ebola virus disease is only moderately so. COVID-19 spreads in the air via droplets and aerosols, whereas when this disease is so hard to identify, there was little scope to measure the effectiveness of rules as a check on COVID-19. While Ebola cases and deaths occurred regularly since 2018, self-reported impacts on revenues and access to food from Ebola were limited, but COVID-19 despite fewer reported cases produced sizable effects on livelihoods, especially in urban areas.

Pandemic Risk and Future Preparedness

While 2026 is not inherently more dangerous than other years, several assessments suggest the world may be entering it less prepared than in the immediate aftermath of COVID-19. Scientists believe the next major threat is most likely to emerge from one of roughly 25 viral families already known to infect humans.

Outbreaks are becoming more frequent and more severe, with the WHO detecting almost twice as many health emergency events in 2024 compared to 2015. The extraordinary improvements and achievements in vaccine development identified in the past few years have been highly successful and are a reassurance that when the next pandemic occurs, we should be able to respond even faster—thanks to the lessons learned from COVID-19.

Final Note

Information about vaccine science, epidemic modeling, and pandemic preparedness is constantly evolving as new data becomes available. For the most current information on vaccine development, disease transmission, or pandemic risk assessment, consult official public health authorities such as the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and your country's health ministry. The scientific understanding of how quickly pandemics might recur or how well current measures protect future populations remains an active area of research and expert debate.

References

• 1. Vaccine science: How are vaccines made? | Children's Hospital of Philadelphia
• 2. How Vaccines Work: The Science Behind Immunization
• 3. Vaccine - Wikipedia
• 4. How do vaccines work?
• 5. The Biology of Vaccines | Johns Hopkins | Bloomberg School of Public Health
• 6. Vaccines | Johns Hopkins Medicine
• 7. How Vaccines Work - Immunology Explained
• 8. Explaining How Vaccines Work | CDC
• 9. Explaining How Vaccines Work | Vaccines & Immunizations | CDC
• 10. The development of COVID-19 vaccines in the United States: Why and how so fast? - PMC