Racing a Pandemic: Alexis Kalergis, Chile's Homegrown COVID-19 Vaccine, and How It Compares to the mRNA Sprint

When SARS-CoV-2 emerged in early 2020, Chile did not just wait for a vaccine to arrive from somewhere else. Alexis Kalergis, an immunologist at the Pontificia Universidad Católica de Chile and director of the Millennium Institute on Immunology and Immunotherapy, pivoted his lab toward the new virus almost immediately — and, separately, took charge of the clinical trials that got an existing vaccine authorized and distributed across Chile within about a year. Comparing his path to the one taken by Pfizer-BioNTech and Moderna in the United States is a good way to see what actually makes vaccine development fast: it's rarely a single breakthrough, and almost always a head start.

Building on 15 years, not starting from zero

Kalergis's lab did not begin thinking about vaccines in 2020. For about 15 years before the pandemic, his team had been developing a vaccine against respiratory syncytial virus (RSV), the leading cause of respiratory illness in infants, and it is the only RSV vaccine in the world designed to be given from birth. That work led to a second vaccine against human metapneumovirus. Both projects gave the lab a working platform, trained staff, and lab infrastructure to build on rather than invent from scratch.

Starting in January 2020, that team redirected the same approach toward SARS-CoV-2: rather than using the whole virus or its genetic material, they selected specific viral proteins and protein fragments — chosen for their ability to trigger a strong, targeted immune response without excessive inflammation — and paired them with molecules that boost that response (an adjuvant). This is called a recombinant protein subunit vaccine. The team also incorporated ideas from their own prior research on "trained immunity," a form of enhanced innate immune readiness. By 2021 they had four candidate formulations in testing.

Two different Chilean vaccine stories, running side by side

It's easy to conflate two separate things Kalergis was doing at once, and a precise answer keeps them apart. First, his own lab's recombinant protein candidate went through the standard pipeline: design, animal testing, then a Phase 1 human trial testing safety and immune response in a small group of volunteers, published in late 2021 and early 2022. As of the most recent public reporting, it had not progressed to large-scale Phase 3 trials or mass production — a reminder that building a genuinely new, homegrown vaccine, even with a 15-year head start, is slow.

Second, and separately, Kalergis coordinated and directed Chile's Phase 3 clinical trial of CoronaVac, an inactivated SARS-CoV-2 vaccine developed and manufactured by the Chinese company Sinovac. That trial — run at eight sites across Chile — generated the safety and efficacy data Chilean regulators needed to authorize the vaccine and gave the country priority access to doses, enabling a mass vaccination campaign in early 2021. Kalergis and his team did not invent CoronaVac; they ran the local trial that got an already-developed, already-mass-manufactured vaccine into Chilean arms quickly. That distinction — running a trial for an existing vaccine versus designing a new one — explains most of the difference in how "fast" each project looks.

How the U.S. mRNA vaccines moved even faster

Pfizer-BioNTech and Moderna also weren't starting from zero. Both companies had spent roughly a decade developing mRNA vaccine platforms for other diseases before 2020; when SARS-CoV-2's genetic sequence was published on January 11, 2020, BioNTech's "Project Lightspeed" began within days, and Moderna moved almost as quickly using the same platform logic Kalergis used with RSV — reuse infrastructure instead of building it new.

What made the U.S. process even faster than Chile's homegrown effort was not just the mRNA platform itself, but how the pipeline was run. Under Operation Warp Speed, the government funded manufacturing "at risk" — meaning companies produced millions of doses before trials even finished, so doses were ready to ship the moment authorization came through. Clinical trial phases were run in overlapping stages rather than waiting for each phase to fully wrap up before starting the next. Both companies began Phase 3 trials on the same day, July 27, 2020, and both received FDA emergency use authorization by the end of December 2020 — under a year from sequence to shots in arms, compared with a typical vaccine development timeline of five to ten years or more.

Same enemy, three different vaccines

All three vaccines discussed here train the immune system to recognize SARS-CoV-2, but they show it a different piece of the virus and in a different form. mRNA vaccines (Pfizer-BioNTech, Moderna) deliver genetic instructions, wrapped in a lipid nanoparticle, that tell a person's own cells to build the viral spike protein temporarily; this produces a strong antibody and T-cell response but tends to come with more reactogenicity (fever, fatigue, injection-site pain), especially after a second or third dose. Inactivated-virus vaccines (CoronaVac) grow real SARS-CoV-2 in the lab and chemically kill it so it can no longer replicate but still displays its full set of viral proteins, not just the spike; this uses decades-old, well-established manufacturing methods and tends to cause milder side effects. Recombinant protein subunit vaccines (Kalergis's candidate, and China's ZF2001) skip live virus and genetic material entirely, manufacturing only a chosen fragment of the spike protein and pairing it with an adjuvant — a strategy with a long safety track record (it's how the hepatitis B vaccine works) but one that generally takes longer to design and produce because the protein has to be grown and purified rather than synthesized directly from a genetic sequence.

What we still don't know: chasing a moving target

Every vaccine discussed here was designed against earlier versions of SARS-CoV-2's spike protein, and the virus has kept mutating that same region ever since, which is why boosters have needed repeated updates. Researchers are now trying to design "pan-coronavirus" or universal vaccines that target parts of the virus that stay the same across variants, but identifying those conserved regions while still triggering strong, lasting protection remains an unsolved design problem. Related open questions include whether nasal or other mucosal vaccines could block infection and transmission at the point of entry rather than mainly preventing severe disease, how durable protection from each vaccine platform really is over multiple years, and whether future vaccines should keep chasing the newest variant every year (as flu vaccines do) or aim for broader, longer-lasting protection instead.

Do we still need to vaccinate? What "herd immunity" means for a shifting virus

Herd immunity is the idea that once enough of a population is immune, a virus can no longer find enough new hosts to keep spreading, which indirectly protects even unvaccinated people. That concept works well for a virus like measles, which barely changes and produces long-lasting immunity after infection or vaccination. SARS-CoV-2 doesn't fit that pattern as cleanly: it continues to evolve into new variants that partially evade immunity built from earlier infection or vaccination, and protection against infection (though less so against severe illness) fades over time in most people. Current estimates suggest the U.S. is near the roughly 70% immunity threshold once considered the herd-immunity target, largely through some combination of vaccination and prior infection, but because the virus keeps changing, that may never translate into the lasting, measles-like herd immunity the term originally described.

That's part of why current U.S. guidance (as of the 2025–2026 season) no longer recommends COVID-19 vaccination for everyone as a blanket rule. Instead, the CDC frames it as an individual, risk-based decision: vaccination is most strongly recommended for adults 65 and older, young infants, people who are immunocompromised, and others at elevated risk of severe disease, while the benefit is smaller for people not in those groups. In other words, the honest answer to "do we still need to vaccinate as much now?" isn't a simple yes or no about herd immunity being reached — it's that the calculation has shifted from a population-wide goal to a personal risk-and-benefit decision.

Recombinant protein subunit vaccine

A vaccine made from a lab-produced fragment of a pathogen's protein (rather than the whole virus or its genetic code), usually combined with an adjuvant to boost the immune response.

Inactivated vaccine

A vaccine made from a whole virus that has been chemically killed so it can no longer replicate, but still displays its proteins to the immune system.

mRNA vaccine

A vaccine that delivers genetic instructions (mRNA), protected in a lipid nanoparticle, that direct a person's own cells to temporarily produce a viral protein and trigger an immune response.

Adjuvant

A substance added to a vaccine to strengthen and prolong the immune response to the antigen it's paired with.

Herd immunity

The indirect protection of a population that occurs when enough individuals are immune to a pathogen that its spread is substantially slowed or stopped, even among those who aren't immune.

Phase 1 / Phase 3 clinical trial

Stages of human testing required before a vaccine can be approved: Phase 1 tests safety and immune response in a small group; Phase 3 tests large-scale efficacy and safety in thousands of participants.

Check your understanding

Background sources to verify and cite before publishing: Pontificia Universidad Católica de Chile, "The Vaccine Against Covid-19 Being 'Made in Chile'" (uc.cl); Cell Press, 50 Inspiring Scientists profile of Alexis M. Kalergis (cell.com); phase I clinical trial of recombinant dimeric RBD COVID-19 vaccine candidates (PMC, medRxiv); ClinicalTrials.gov NCT04651790 (Chile CoronaVac Phase 3 trial); New England Journal of Medicine, "Developing Safe and Effective Covid Vaccines — Operation Warp Speed's Strategy and Approach"; GAO-21-319 on Operation Warp Speed; Frontiers in Immunology comparison of immune responses to mRNA vs. recombinant protein COVID-19 vaccines; CDC, 2025–2026 COVID-19 Vaccination Guidance (cdc.gov); Rochester Regional Health, "What Herd Immunity for COVID-19 Means In 2026"; recent reviews on universal/pan-coronavirus vaccine design challenges (Vaccines, Pathogens journals).