2021 was the year the COVID-19 vaccines had to prove their mettle. We started the year full of hope: With vaccines in hand in record-breaking time and their rollout ramping up, we’d get shots in arms, curb this pandemic and get life back to normal. That was too optimistic.
Roughly 200 million people in the United States — and billions globally — have now been fully vaccinated. Three vaccines — one from Pfizer and its partner BioNTech, and the other two from Moderna and Johnson & Johnson — are available in the United States. Pfizer’s is even available for children as young as 5. About two dozen other vaccines have also been deployed in other parts of the world. In some higher-income countries, the United States included, people have already queued up for booster shots.
But 2021 has also been the year of learning the limits of the vaccines’ superpowers. With the vaccines pitted against aggressive coronavirus variants, inequitable distribution, some people’s hesitancy and the natural course of waning effectiveness, there’s still a lot of work to do to bring this pandemic to an end. As if to hammer home that point, the detection of the omicron variant in late November brought new uncertainty to the pandemic’s trajectory. Here are some of the top lessons we’ve learned in the first year of the COVID-19 vaccine. — Macon Morehouse
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The shots work, even against emerging variants
Many COVID-19 vaccines proved effective over the last year, particularly at preventing severe disease and death (SN: 10/9/21 & 10/23/21, p. 4). That’s true even with the emergence of more transmissible coronavirus variants.
In January, in the midst of a bleak winter surge that saw average daily cases in the United States peaking at nearly 250,000, the vaccination rollout here began in earnest. Soon after, case numbers began a steep decline.
Over the summer, though, more reports of coronavirus infections in vaccinated people began to pop up. Protection against infection becomes less robust in the months following vaccination in people who received Pfizer’s or Moderna’s mRNA vaccines, multiple studies have shown (SN Online: 9/21/21). Yet the shots’ original target — preventing hospitalization — has held steady, with an efficacy of about 80 percent to 95 percent.
A single dose of Johnson & Johnson’s vaccine is less effective at preventing symptoms or keeping people out of the hospital than the mRNA jabs. The company claims there’s not yet evidence that the protection wanes. But even if that protection is not waning, some real-world data hint that the shot may not be as effective as clinical trials suggested (SN Online: 10/19/21).
Evidence of waning or lower protection ultimately pushed the United States and some other countries to green-light COVID-19 booster shots for adults (SN: 12/4/21, p. 6).
Much of the worry over waning immunity came amid the spread of highly contagious variants, including alpha, first identified in the United Kingdom in September 2020, and delta, first detected in India in October 2020 (SN Online: 7/30/21). Today, delta is the predominant variant globally.
The good news is that vaccinated people aren’t unarmed against these mutated foes. The immune system launches a multipronged attack against invaders, so the response can handle small molecular tweaks to viruses, says Nina Luning Prak, an immunologist at the University of Pennsylvania. Dealing with variants “is what the immune system does.”
But it’s unlikely that any new variant will take us back to square one, Çevik says. Because of the immune system’s varied defenses, it will be difficult for a coronavirus variant to become completely resistant to vaccine-induced protection. The vaccines are giving our immune systems the tools to fight back. — Erin Garcia de Jesús
The shots are safe, with few serious side effects
With billions of doses distributed around the world, the shots have proved not only effective, but also remarkably safe, with few serious side effects.
“We have so much safety data on these vaccines,” says Kawsar Talaat, an infectious diseases physician at the Johns Hopkins Bloomberg School of Public Health. “I don’t know of any vaccines that have been scrutinized to the same extent.”
Commonly reported side effects include pain, redness or swelling at the spot of the shot, muscle aches, fatigue, fever, chills or a headache. These symptoms usually last only a day or two.
More rare and serious side effects have been noted. But none are unique to these shots; other vaccines — plus infectious diseases, including COVID-19 — also cause these complications.
One example is inflammation of the heart muscle, known as myocarditis, or of the sac around the heart, pericarditis. Current estimates are a bit squishy since existing studies have different populations and other variables (SN Online: 10/19/21). Two large studies in Israel estimated that the risk of myocarditis after an mRNA vaccine is about 4 of every 100,000 males and 0.23 to 0.46 of every 100,000 females, researchers reported in October in the New England Journal of Medicine. Yet members of Kaiser Permanente Southern California who had gotten mRNA vaccines developed myocarditis at a much lower rate: 5.8 cases for every 1 million second doses given, researchers reported, also in October, in JAMA Internal Medicine.
What all the studies have in common is that young males in their teens and 20s are at highest risk of developing the side effect, and that risk is highest after the second vaccine dose (SN Online: 6/23/21). But it’s still fairly rare, topping out at about 15 cases for every 100,000 vaccinated males ages 16 to 19, according to the larger of the two Israeli studies. Males in that age group are also at the highest risk of getting myocarditis and pericarditis from any cause, including from COVID-19.