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Study shows why second dose of COVID-19 vaccine shouldn’t be skipped

The second dose of a COVID-19 vaccine induces a powerful boost to a part of the immune system that provides broad antiviral protection, according to a study led by investigators at the Stanford University School of Medicine.

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The second dose of a COVID-19 vaccine induces a powerful boost to a part of the immune system that provides broad antiviral protection, according to a study led by investigators at the Stanford University School of Medicine.

The finding strongly supports the view that the second shot should not be skipped.

“Despite their outstanding efficacy, little is known about how exactly RNA vaccines work,” said Bali Pulendran, PhD, professor of pathology and of microbiology and immunology. “So we probed the immune response induced by one of them in exquisite detail.”

The study, published in Nature, was designed to find out exactly what effects the vaccine, marketed by Pfizer Inc., has on the numerous components of the immune response.

The researchers analyzed blood samples from individuals inoculated with the vaccine. They counted antibodies, measured levels of immune-signaling proteins and characterized the expression of every single gene in the genome of 242,479 separate immune cells’ type and status.

“The world’s attention has recently been fixed on COVID-19 vaccines, particularly on the new RNA vaccines,” said Pulendran, the Violetta L. Horton Professor II.

He shares senior authorship of the study with Kari Nadeau, MD, PhD, the Naddisy Foundation Professor of Pediatric Food, Allergy, Immunology, and Asthma and professor of pediatrics, and Purvesh Khatri, PhD, associate professor of biomedical informatics and of biomedical data science. The study’s lead authors are Prabhu Arunachalam, PhD, a senior research scientist in Pulendran’s lab; medical student Madeleine Scott, PhD, a former graduate student in Khatri’s lab; and Thomas Hagan, PhD, a former postdoctoral scholar in Pulendran’s Stanford lab and now an assistant professor at the Yerkes National Primate Research Center in Atlanta.

Uncharted territory

“This is the first time RNA vaccines have ever been given to humans, and we have no clue as to how they do what they do: offer 95% protection against COVID-19,” said Pulendran.

Traditionally, the chief immunological basis for approval of new vaccines has been their ability to induce neutralizing antibodies: individualized proteins, created by immune cells called B cells, that can tack themselves to a virus and block it from infecting cells.

“Antibodies are easy to measure,” Pulendran said. “But the immune system is much more complicated than that. Antibodies alone don’t come close to fully reflecting its complexity and potential range of protection.”

Pulendran and his colleagues assessed goings-on among all the immune cell types influenced by the vaccine: their numbers, their activation levels, the genes they express and the proteins and metabolites they manufacture and secrete upon inoculation.

One key immune-system component examined by Pulendran and his colleagues was T cells: search-and-destroy immune cells that don’t attach themselves to viral particles as antibodies do but rather probe the body’s tissues for cells bearing telltale signs of viral infections. On finding them, they tear those cells up.

In addition, the innate immune system, an assortment of first-responder cells, is now understood to be of immense importance. It’s the body’s sixth sense, Pulendran said, whose constituent cells are the first to become aware of a pathogen’s presence. Although they’re not good at distinguishing among separate pathogens, they secrete “starting gun” signaling proteins that launch the response of the adaptive immune system — the B and T cells that attack specific viral or bacterial species or strains. During the week or so it takes for the adaptive immune system to rev up, innate immune cells perform the mission-critical task of holding incipient infections at bay by gobbling up — or firing noxious substances, albeit somewhat indiscriminately, at — whatever looks like a pathogen to them.

A different type of vaccine

The Pfizer vaccine, like the one made by Moderna Inc., works quite differently from the classic vaccines composed of live or dead pathogens, individual proteins or carbohydrates that train the immune system to zero in on a particular microbe and wipe it out. The Pfizer and Moderna vaccines instead contain genetic recipes for manufacturing the spike protein that SARS-CoV-2, the virus that causes COVID-19, uses to latch on to cells it infects.

In December 2020, Stanford Medicine began inoculating people with the Pfizer vaccine. This spurred Pulendran’s desire to assemble a complete report card on the immune response to it.

The team selected 56 healthy volunteers and drew blood samples from them at multiple time points preceding and following the first and second shots. The researchers found that the first shot increases SARS-CoV-2-specific antibody levels, as expected, but not nearly as much as the second shot does. The second shot also does things the first shot doesn’t do, or barely does.

“The second shot has powerful beneficial effects that far exceed those of the first shot,” Pulendran said. “It stimulated a manifold increase in antibody levels, a terrific T-cell response that was absent after the first shot alone, and a strikingly enhanced innate immune response.”

Unexpectedly, Pulendran said, the vaccine — particularly the second dose — caused the massive mobilization of a newly discovered group of first-responder cells that are normally scarce and quiescent.

First identified in a recent vaccine study led by Pulendran, these cells — a small subset of generally abundant cells called monocytes that express high levels of antiviral genes — barely budge in response to an actual COVID-19 infection. But the Pfizer vaccine induced them.

This special group of monocytes, which are part of the innate museum, constituted only 0.01% of all circulating blood cells prior to vaccination. But after the second Pfizer-vaccine shot, their numbers expanded 100-fold to account for a full 1% of all blood cells. In addition, their disposition became less inflammatory but more intensely antiviral. They seem uniquely capable of providing broad protection against diverse viral infections, Pulendran said.

“The extraordinary increase in the frequency of these cells, just a day following booster immunization, is surprising,” Pulendran said. “It’s possible that these cells may be able to mount a holding action against not only SARS-CoV-2 but against other viruses as well.”

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Scheduling dental care during prenatal visits boosts oral health care during pregnancy

Scheduling a dental appointment during prenatal clinic visits—a simple, no-cost task that doesn’t require extra staff—increases the likelihood that patients later see a dentist during pregnancy.

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Prenatal visits might include bloodwork, discussions of due dates and vitamins, and ultrasounds. What if these visits could also improve oral health care among pregnant patients?

New research shows that scheduling a dental appointment during prenatal clinic visits—a simple, no-cost task that doesn’t require extra staff—increases the likelihood that patients later see a dentist during pregnancy.

The study, published in the American Journal of Public Health, demonstrates the benefit of coordination among health providers and integrating oral health into prenatal care, especially for vulnerable patient populations.

Historically, dentists avoided treating women during pregnancy unless it was an emergency, or only provided care during the second trimester. This guidance changed once studies showed that routine and emergency dental care is safe during pregnancy—and current obstetric and dental guidelines stress that dental care can and should be provided during this critical period.

Moreover, pregnancy increases the risk of some oral health conditions, including gum inflammation and sometimes tooth decay, making routine dental care even more important during pregnancy. Some oral health issues may affect the fetus or even be transmissible to the child after birth. 

Marginalized groups, including low-income individuals and those insured by Medicaid, are known to have higher rates of dental disease. Yet women enrolled in Medicaid are far less likely to see a dentist for a cleaning during pregnancy compared to women with private insurance.

“Many of those vulnerable to oral disease enter pregnancy with dental disease, and this may worsen during pregnancy,” said study author Stefanie Russell, associate professor at Rutgers School of Dental Medicine and an adjunct associate professor at NYU College of Dentistry, who led this research while at NYU.

One way to try and increase dental care among pregnant women is to reach them where they already are: their prenatal appointments. To bridge this gap, researchers and clinicians at NYU College of Dentistry teamed up with neighboring NYC Health + Hospitals/Bellevue, the oldest public hospital in the US, to create the New York University/Bellevue Prenatal Oral Health Program. 

During weekly sessions at Bellevue’s prenatal clinic, pregnant patients receive a standardized screening to assess their oral health. Those with dental needs are referred to NYU College of Dentistry for follow-up care, educated about the importance and safety of dental care during pregnancy, and informed that Medicaid covers dental care in New York.

From 2018 to 2020, 420 prenatal patients with Medicaid coverage were referred to NYU Dentistry for follow-up dental care; the majority were Hispanic, and roughly half spoke Spanish as their first language. Referrals for dental care took two forms: immediately scheduled dental appointments made before the patient left the prenatal clinic or through a patient navigator. The patient navigator—a bilingual professional—educated patients regarding oral health, reminded patients of their upcoming dental appointments, and followed up after to identify any issues. 

Nearly 44 percent of patients referred to NYU College of Dentistry followed through with a dental appointment. Both immediate appointment scheduling and the patient navigator increased the chances of a patient receiving dental care, but those who had appointments scheduled at their prenatal visit were 2.6 times more likely to see a dentist than those without appointments scheduled—even more likely than those who worked with the patient navigator.

“This suggests that immediately scheduled dental appointments can be an effective way to increase dental care utilization during pregnancy, without needing to hire extra staff,” said study author Shulamite Huang, assistant professor of epidemiology and health promotion at NYU College of Dentistry.

The authors conclude that integrating oral health screening in a prenatal clinic is feasible and increases engagement with dental care during pregnancy. They are continuing their research to measure whether this care improves oral health outcomes and to better understand how dental screening can be successfully integrated with prenatal care in other settings.

“A warm hand-off is key for addressing part of the barriers to dental care during pregnancy. Our team plans to further investigate and optimize interventions addressing both patient-, provider-, and healthcare system-level barriers to dental care during pregnancy,” said Huang.  

Additional study authors include Richard Heyman and Mary Kang of NYU Dentistry; Belkys Saba, formerly of NYU Dentistry; Chloe Bird of the Tufts University School of Medicine; and Chengwu Yang of the Florida Atlantic University Schmidt College of Medicine.

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Why a UTI hurts — and why that might be a good thing

Australian researchers have discovered a previously overlooked group of bladder nerves that help detect urinary tract infections (UTIs) and trigger the body’s response to clear them, providing a potential new target for future bladder pain therapies.

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Australian researchers have discovered a previously overlooked group of bladder nerves that help detect urinary tract infections (UTIs) and trigger the body’s response to clear them, providing a potential new target for future bladder pain therapies.

The study shows that bladder nerves located close to the lining of the bladder act as a frontline infection sensor, helping the body recognise UTIs and trigger responses that reduce the severity and spread of infection.

UTIs are among the most common bacterial infections worldwide, with more than 400 million cases reported every year. Nearly one in three women will experience UTIs before the age of 24, and many elderly people and those with bladder issues from spinal cord injuries can experience multiple UTIs in a single year.

Symptoms often include frequent urination, a sudden urge to urinate, pain during urination, and pelvic discomfort can be debilitating for some patients.

Flinders University’s Dr Luke Grundy says that while scientists have long understood how the bladder senses as it fills and triggers urination, the role of a specialised group of bladder nerves near the bladder lining has remained unclear.

“Most bladder nerves act like a fuel gauge, telling the brain when the bladder is filling up and needs emptying,” says Dr Grundy, Head of the NeuroUrology Research Group at Flinders University.

“The nerves we studied in this research are different. They sit close to the bladder lining and appear to act more like an early warning system, detecting infection and inflammation.

“They don’t just sense infection. They help coordinate the body’s response to it by triggering pain and urinary frequency, behaviours that appear to help clear bacteria from the bladder as part of the body’s defence system.”

Lead author and recently graduated PhD student Dr Cindy Tay says the discovery changes how these nerves are understood.

“These mucosal nerves have puzzled scientists for almost two decades because they stay quiet while the bladder fills and empties, which is the main job of the bladder,” says Dr Tay.

“What we’ve found is that they have a hidden job — acting as an early warning system that springs into action the moment infection takes hold.”

The research team developed a novel method to selectively study a specialised group of sensory nerves in the bladder lining of mice, revealing that while these nerves play little role in normal bladder function, they become highly responsive during a UTI and help detect and respond to infection.

“When the bladder is healthy, these nerves are relatively quiet, but during a urinary tract infection they become highly sensitive and respond to the presence of bacteria and inflammation,” says Dr Grundy.

“It may feel unpleasant, but urinating more frequently actually helps clear the infection by flushing out the harmful bacteria.”

The study also helps explain why people with conditions affecting nerve function may be more prone to recurrent or severe UTIs.

“If the nerves that detect infection aren’t working properly, the body may not respond as effectively,” says Dr Grundy.

Building on previous research, the new study reveals a deeper understanding of how UTIs affect bladder function and the nervous system, and could help develop new treatments that target these nerves to relieve UTI-related symptoms.

“Our findings provide new insight into how the bladder detects and responds to infection, helping explain the biological processes that drive the pain, urgency and discomfort commonly experienced during UTIs,” says Dr Grundy

Researchers say the next challenge is to develop therapies that ease the pain and urgency associated with UTIs while preserving the protective role these nerves play in fighting infection.

The paper, ‘Bladder mucosal afferents detect UTI and aid pathogen clearance,’ by Cindy Tay, Harman Sharma, Stewart Ramsay (University of Adelaide), Georgia Bourlotos, Sarah K Manning, Natalie E Stevens, Sophie J Miller, Geraint B Rogers, David J Lynn, Feargal J Ryan, Andrea M Harrington (University of Adelaide), Vladimir Zagorodnyuk, Steven L Taylor and Luke Grundy was published in Proceedings of the National Academy of Sciences (PNAS).

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Pregnancy complications can signal heart disease risk years before traditional screening, study finds

Some women, particularly younger women often considered low risk, may face a higher risk of heart disease earlier than previously recognized.

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McGill University researchers have developed a new tool to identify heart disease risk in women earlier in life.

Findings from a study published in JACC: Advances highlight gaps in existing approaches.

“Heart disease is the leading cause of death in women, yet existing risk tools were developed in older populations and ignore factors unique to women,” said senior author Robert Platt, Professor in the Department of Epidemiology, Biostatistics, and Occupational Health and Director of the School of Population and Global Health.

While pregnancy complications are known to be linked to future heart risk, there has been no way to identify which younger women are most at risk, he added.

Detecting risk earlier

Using health data from more than 260,000 women in the UK aged 15 to 45 who had given birth, researchers developed and validated a prediction model to estimate future heart disease risk. Participants were followed for nearly four years after delivery.

The model identified several factors – not included in existing tools – that can help predict risk, including hypertensive disorders of pregnancy, gestational diabetes, preterm birth, PCOS, depression, thyroid disorders, oral contraceptive use and social deprivation.

The findings suggest some women, particularly younger women often considered low risk, may face a higher risk of heart disease earlier than previously recognized.

“Millions of women who give birth each year are never considered candidates for cardiovascular risk assessment simply because of their age,” said co-author Kristian Filion, Professor in the Departments of Medicine and of Epidemiology, Biostatistics, and Occupational Health.

If integrated into routine postpartum care, this tool could enable earlier monitoring, lifestyle counselling or referral to a specialist, potentially helping prevent a heart attack or stroke later in life, he added.

The next step is to validate the model in Canada and the United States. In the longer term, the goal is to integrate a practical calculator into electronic health records so higher-risk patients can be identified earlier.

About the study

Development and Validation of a Prediction Model for Cardiovascular Risk in Reproductive-Aged Women” by Sonia Grandi, Kristian Filion, Jennifer Hutcheon, Graeme Smith, and Robert Platt was published in JACC: Advances. The study was supported by the Canadian Institutes of Health Research.

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