How long are COVID-19 vaccines effective?

Ukrainian Health Minister Maksym Stepanov speaks with Anna Ilina, a member of the Ukrainian Olympic shooting team that will compete in the Tokyo 2020 Olympics, as she waits before receiving a dose of Chinese-developed CoronaVac vaccine against the coronavirus disease (COVID-19) in Kyiv, Ukraine April 15, 2021. REUTERS/Valentyn Ogirenko - RC29WM9FP122

Ukraine's health minister and a member of the Ukrainian Olympic shooting team before she receives a dose of COVID-19 vaccine in Kyiv, April 15, 2021. Image: REUTERS/Valentyn Ogirenko - RC29WM9FP122

John Letzing
Digital Editor, World Economic Forum
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  • Experts don’t know yet how long COVID-19 vaccines will be effective.
  • Studies of two of the most prominent COVID-19 vaccines suggest they remain effective for at least six months.
  • The CEO of one vaccine maker said immunity may start to fade within a year.

One of the most pressing questions about COVID-19 vaccines is how long they can provide protection.

It may be decades, or a matter of months – the data necessary to figure that out is accumulating every day. Pfizer’s CEO said this week that after a full regimen of doses immunity will probably start to fade within a year. According to the WHO, it’s simply too early to know the exact duration of COVID-19 vaccines because both the disease and the science deployed against it aren’t yet fully understood.

Some early evidence is promising. The viruses that caused MERS and SARS are closely related to the virus behind COVID-19, and acquired immunity to both of those diseases has proved relatively durable.

In terms of COVID-19-specific research, Pfizer and BioNTech said earlier this month that their vaccine remains effective for at least half a year after the second dose, and a study of Moderna’s version reflected a similar duration. Immunization efforts will have to play out further before we can know more for certain.

The window of immunity enabled by vaccines could have an impact on efforts to fully re-open the global economy, and re-establish a sense of normalcy. For now, though, much of the focus has been on getting that first dose into arms, something many countries are still waiting for.

Though criticism has mounted of the pace of vaccinations in Europe, the region is still clearly better off than much of the world. In the image below, countries turn a progressively darker green as the share of their population fully vaccinated against COVID-19 increases through 13 April. The fully-darkened countries are where no related data were available yet.

US date format.
US date format. Image: World Economic Forum

People from wealthier countries who’ve been at the front of the line for vaccines have instantly become test subjects for assessing duration.

Booster shots could help address what will likely be a slow decline of immunity over time. In this way, COVID-19 may look a lot like the flu – which also produces variants, and can be addressed with a yearly shot formulated to deal with the latest mutations.

Historically, other diseases have been quelled at least in part thanks to surprisingly lasting periods of immunity. Memory B cells needed to protect against being re-infected with the deadly Spanish flu that spread around the world in 1918 endured for nearly 90 years, according to one study.

And research has suggested that memory B cells necessary to protect against re-infection with smallpox last about 60 years following immunization.

Relatively shorter periods of established immunity won’t diminish a COVID-19 vaccine development effort that’s widely recognized as an extraordinary achievement – and should only increase the public’s faith in the positive impact of science.

Image: World Economic Forum

For more context, here are links to further reading from the World Economic Forum's Strategic Intelligence platform:

  • The messaging surrounding COVID-19 vaccines is as important as the science behind them, according to this analysis – and that’s certainly true when it comes to explaining why the US recently paused the Johnson & Johnson vaccine following reports of extremely rare side effects. (Kaiser Health News)
  • Even if they had abundant access to vaccines, would some Europeans take them? France, home to Louis Pasteur and a universal health care system, has somehow also become home to a surprising degree of vaccine hesitancy, according to this report. (The Atlantic)
  • Bhutan’s first vaccine dose was administered to a woman born in the Year of the Monkey amid chants of Buddhist prayers in late March, according to this report. Since then, the country has managed to vaccinate more than 93% of its adult population. (The Diplomat)
  • For many of us, it’s hard to feel the momentousness of the season through which we’re now living, according to this piece – in the 1950s Americans were unabashedly jubilant about the vanquishing of polio, but they're strangely uncertain in their celebration of new vaccines. (New Yorker)
  • Hear directly from experts: this virtual panel of scientists recently addressed questions about vaccines including how they work, how they were developed, and the potential need for boosters. (Cornell University)
  • A tiny number of people will be hospitalized despite being vaccinated. Experts say we should investigate who’s most vulnerable to these “breakthrough infections,” but according to this piece, that’s often not happening. (ProPublica)
  • Vaccinate billions or lose the battle for democracy – the EU and G7 are in strong positions to lead a truly global effort to vaccinate the world, according to this analysis, but that will mean taking a hard look at patents. (Carnegie Endowment for International Peace)

On the Strategic Intelligence platform, you can find feeds of expert analysis related to Vaccination, Science and hundreds of additional topics. You’ll need to register to view.

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