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A 62-year-old man in Germany decided to get 217 COVID-19 vaccinations over the course of 29 months —for "private reasons." But, somewhat surprisingly, he doesn't seem to have suffered any ill effects from the excessive immunization, particularly weaker immune responses, according to a newly published case study in The Lancet Infectious Diseases .

The case is just one person, of course, so the findings can't be extrapolated to the general population. But, they conflict with a widely held concern among researchers that such overexposure to vaccination could lead to weaker immune responses. Some experts have raised this concern in discussions over how frequently people should get COVID-19 booster doses.

In cases of chronic exposure to a disease-causing germ, "there is an indication that certain types of immune cells, known as T-cells, then become fatigued, leading to them releasing fewer pro-inflammatory messenger substances," according to co-lead study author Kilian Schober from the Institute of Microbiology – Clinical Microbiology, Immunology and Hygiene. This, along with other effects, can lead to "immune tolerance" that leads to weaker responses that are less effective at fighting off a pathogen, Schober explained in a news release.

Enlarge / Heart scan. (credit: Getty | BSIP )

The mRNA-based COVID-19 vaccines have proven remarkably safe and effective against the deadly pandemic. But, like all medical interventions, they have some risks. One is that a very small number of vaccinated people develop inflammation of and around their heart—conditions called myocarditis, pericarditis, or the combination of the two, myopericarditis. These side effects mostly strike males in their teens and early 20s, most often after a second vaccine dose. Luckily, the conditions are usually mild and resolve on their own.

With the rarity and mildness of these conditions, studies have concluded, and experts agree that the benefits of vaccination outweigh the risks—male teens and young adults should get vaccinated. In fact, they're significantly more likely to develop myocarditis or pericarditis from a COVID-19 infection than from a COVID-19 vaccination. According to a large 2022 study led by researchers at Harvard University and the Centers for Disease Control and Prevention, the group at highest risk of myocarditis and pericarditis after vaccination—males aged 12 to 17—saw 35.9 cases per 100,000 (0.0359 percent) after a second vaccine dose, while the rate was nearly double after a COVID-19 infection in the same age group, with 64.9 cases per 100,000 (0.0649 percent)

Still, the conditions are a bit of a puzzle. Why do a small few get this complication after vaccination? Why does it seem to solely affect the heart? How does the damage occur? And what does it all mean for the many other mRNA-based vaccines now being developed?

Enlarge (credit: Getty | Future Publishing )

The new bivalent COVID-19 booster spurred neutralizing antibody levels that were fourfold higher against the omicron subvariants BA.4/BA.5 in older adults than those seen after the original booster, Pfizer reported Friday .

The new data may help calm concerns about whether the updated booster is an improvement over the previous booster. But the fall booster campaign—aimed at preventing another devastating winter wave—still faces considerable challenges. For one thing, a shockingly low number of Americans are rolling up their sleeves to get the shot.

Better boost

Experts all agree that the new booster shot, like the old one, will revive waning immune responses to SARS-CoV-2 and provide strong protection from severe COVID-19. But some experts have expressed skepticism about whether the updated bivalent booster—which in part targets omicron subvariants BA.4/BA.5—will offer a clinically meaningful advantage over the previous booster in preventing mild infections against the subvariant.

Enlarge / A man receives an H1N1 nasal flu spray vaccine at an urgent care center on October 16, 2009, in Lake Worth, Florida. (credit: Getty | Joe Raedle )

The nasal version of the Oxford/AstraZeneca COVID-19 vaccine failed an early-stage clinical trial, dashing hopes for better infection prevention and forcing researchers to re-think the design.

Many experts have hyped the potential of nasal COVID-19 vaccines. They argue that snorting the shots could encrust the nasal mucous membranes with snotty antibodies—namely IgA—and other immune defenses that could blow away SARS-CoV-2 virus particles before they have the chance to cause an infection. Currently, the shots given intramuscularly in arms provide robust systemic immune responses that prevent severe disease and death but spur relatively weak antibody levels on mucous membranes and, relatedly, don't always prevent infection.

Researchers at the University of Oxford hoped to easily adapt their existing COVID-19 vaccine for such an infection-blasting schnoz spritz. The Oxford/AstraZeneca vaccine is a viral vector-based design, using a weakened, benign virus to carry the genetic code of the SARS-CoV-2 spike protein to human cells. The benign virus, in this case, is an adenovirus, a type best known for causing mild cold-like illnesses in humans, though the specific virus used in the vaccine was isolated from chimpanzees. (This vaccine has not been authorized in the US but is used in dozens of countries worldwide.)

Enlarge / A medical worker arranges nucleic acid samples at a makeshift nucleic acid testing site on May 3, 2022 in Beijing, China. (credit: Getty | Pang Songgang )

The omicron subvariant BA.2.12.1 is poised to become dominant in the US, currently accounting for an estimated 36.5 percent of all US SARS-CoV-2 cases, according to the latest estimates released Tuesday by the Centers for Disease Control and Prevention.

The subvariant's ascent is the latest rapid succession of omicron subvariants, from the sky-scraping peak of cases from the initial omicron subvariant BA.1 in January, to the current bump driven by the subvariant BA.2, which achieved dominance in March. As before, the reason for the viral usurping is that omicron subvariants continue to evolve advantages: BA.2.12.1 has a transmission advantage over BA.2, which had a transmission advantage over BA.1, which had a significant advantage over delta.

The imminent reign of BA.2.12.1 raises concern for yet another wave of infections and poses questions about how effective future omicron-specific vaccines could be against symptomatic infections.

Enlarge / A COVID-19 testing tent stands in Times Square on April 27, 2022, in New York City. (credit: Getty | Spencer Platt )

Enduring an initial omicron infection may not spare you from omicron's subvariants, according to preliminary data from South Africa.

The country is currently at the start of a new wave of infections, primarily driven by two omicron coronavirus subvariants, BA.4 and BA.5. Despite a towering wave of cases from the initial BA.1 omicron variant in December that infected a large chunk of the country, new omicron cases increased 259 percent in the last two weeks, according to data-tracking by The New York Times. Hospitalizations are also up, and deaths have increased by 18 percent.

Preliminary data posted online last week helps explain why cases are once again surging—the BA.4 and BA.5 omicron subvariants can evade neutralizing antibodies generated by infections from BA.1. For the study, led by virologist Alex Sigal of the Africa Health Research Institute, researchers pitted neutralization antibodies from people infected with BA.1 up against BA.4 and BA.5 in a lab. They had samples from 24 unvaccinated people infected with BA.1 and 15 vaccinated people who had also had a BA.1 infection (eight people were vaccinated with the Pfizer/BioNTech vaccine, and seven had the Johnson & Johnson vaccine).