COVID-19 vaccines have been around for half a year, what have we learned so far?

One thing we know for sure: they don’t make you magnetic.

Those fortunate enough to receive the first available doses of COVID-19 vaccines have been serving as test subjects. Roughly half a year into this global experiment, what have we learned so far?

There have been some unsettling developments, like the Ugandan Olympic coach who tested positive for COVID-19 after arriving in Japan for the delayed games – and apparently after having been vaccinated (such “breakthrough” infections remain rare).

However, global confirmed cases and deaths have been trending downward since April, and a pair of studies published last month suggest vaccination can indeed provide a plausible path out of the pandemic. Roughly 2.5 billion doses have been administered globally since the first went to a woman in the UK last December.

So far, it’s safe to say, vaccines seem to be working well.

COVID-19 vaccines had saved nearly an estimated 12,000 lives in England alone by last month, China has been vaccinating a population the size of Romania every day, and San Francisco, where nearly 70% of residents had been fully vaccinated as of early this month, has become among the first US cities to achieve herd immunity.

One real-world study published in March of people in Denmark prioritized for the Pfizer-BioNTech vaccine found it was 90% effective among healthcare workers, and 64% effective among residents of long-term care facilities with a median age of 84.

However, troubling variants like “Delta” in India, the UK, and the US have raised questions about their potential resilience to vaccines. A study published in the UK last month found that two doses of the Pfizer-BioNTech vaccine were 88% effective against symptomatic disease from Delta, though epidemiologists have warned that variants could ultimately render current vaccines ineffective in a year or less.

Potential side effects have been another concern. Rare occurrences of a blood-clotting syndrome have been linked to the Oxford-AstraZeneca and Johnson & Johnson vaccines, but experts say the benefits still outweigh the risks.

A fact overshadowing any good news about vaccines is that much of the world hasn’t yet been able to receive any doses at all. One analysis suggested that more than 85 countries, mostly in Africa, won’t have widespread COVID-19 vaccine access before 2023.

Below is a visualization of COVID-19 vaccination doses administered per 100 people between January and May of this year – each country turns white as data becomes available, then progressively darker blue as the number of administered doses increases.

According to the Centers for Disease Control in the US, fully vaccinated people should be able to resume activities without masks (except where mandated), and travel without testing or quarantining. Still, experts caution against gatherings of multiple households without precautions if some people there are unvaccinated.

A study published in April in the UK found that receiving a single dose of the Pfizer-BioNTech or Oxford-AstraZeneca vaccines notably reduced the odds of infecting other household members, and another published last month found that the viral load was significantly diminished for people in Israel infected a couple of weeks past their first dose of Pfizer-BioNTech – making them less infectious to others.

Yet another study published by the US CDC last month showed that two doses of the Pfizer-BioNTech and Moderna vaccines reduced the risk of healthcare workers getting sick with COVID-19 by 94%.

Researchers are still gathering what scant evidence has accumulated so far on how long protection lasts after vaccination. The role of booster shots may start to become clearer in September, when results from a study in England providing boosters to people at least 10 weeks past their second vaccine dose are anticipated.

Unfortunately, a significant number of people remain reluctant to be vaccinated. In the US, recent poll results showed that 24% of adults said they don’t plan to be vaccinated – and 78% of those people were unlikely to reconsider.

Another report published last month found that even though just 64% of adults in the US said they’d gotten at least one vaccine dose or intended to, general enthusiasm about getting vaccinated was reaching a plateau.

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