The apparent benefits of updated COVID-19 vaccines in older adults may be influenced by more than the vaccines themselves, according to a study examining the “healthy vaccinee effect,” a form of bias that can complicate observational research. Published in Nature Communications, the work by Lyth, Spreco, Hinkula and colleagues focuses on how differences between people who receive vaccination and those who do not can alter estimates of vaccine effectiveness, particularly in elderly populations whose health status can change rapidly.

Updated COVID-19 vaccines are designed to improve protection against circulating SARS-CoV-2 variants, especially protection against severe disease, hospitalization and death. Because randomized clinical trials are not usually repeated for every reformulated vaccine and every emerging variant, researchers frequently rely on real-world health data. These studies compare outcomes among vaccinated and unvaccinated people, but the two groups may differ in important ways before vaccination occurs. Such differences can produce an apparent vaccine benefit—or obscure a real one—even when the analysis carefully accounts for age and medical conditions.

The healthy vaccinee effect arises when people who are vaccinated are temporarily healthier, more active or better connected to healthcare services than those who remain unvaccinated. Individuals may postpone vaccination during an acute illness, after hospitalization or when they are approaching the end of life. At the same time, people who attend vaccination appointments may be more likely to receive preventive care, follow medical advice and seek treatment early. These characteristics are not necessarily caused by vaccination, but they can lower the vaccinated group’s risk of death or hospitalization during the period used for analysis.

This issue is particularly important in older populations. Elderly people often have multiple chronic conditions, fluctuating functional status and frequent contact with hospitals or long-term care facilities. A person may be eligible for a vaccine campaign but unable to receive the dose because of an acute health problem. If that person later dies or is hospitalized, conventional analyses may attribute the worse outcome to the absence of vaccination, even though the underlying illness was already present. Conversely, if researchers compare groups immediately after vaccination without accounting for this selection process, the vaccine may appear more protective than it truly is.

The study evaluates how this bias affects assessments of updated COVID-19 vaccines in elderly populations. Its central scientific contribution is to treat vaccination not simply as an exposure, but as an event embedded in a changing health trajectory. The health of older adults is not static: frailty, infection, recent hospitalization and access to care can all influence whether and when vaccination occurs. By examining these time-dependent factors, the researchers draw attention to the difference between a vaccine’s biological effect and the characteristics of the people who are able to receive it at a particular moment.

In epidemiological terms, the healthy vaccinee effect is a form of confounding and selection bias. Confounding occurs when another factor is associated with both vaccination and the outcome being measured. Selection bias occurs when inclusion in the vaccinated or comparison group depends on health-related circumstances. Timing can intensify both problems. If follow-up begins on the day of vaccination for one group but at an arbitrary date for another, the groups may not have equivalent baseline risks. Researchers therefore need to define an appropriate index date, align observation periods and account for recent illness, healthcare use and changes in eligibility.

The challenge is not merely statistical. A vaccine can provide strong protection against severe COVID-19 while producing a smaller or more variable effect against infection, depending on the variant, time since vaccination, prior immunity and the outcome being studied. If an observational analysis reports a lower mortality rate among vaccinated people, that result may reflect a combination of direct vaccine protection and the healthier profile of vaccine recipients. Separating these components requires careful design, including adjustment for measured risk factors and, where possible, comparison strategies that mimic a randomized trial.

The findings have practical implications for interpreting public-health evidence. Estimates of updated vaccine effectiveness should not be read in isolation from the population being studied, the timing of vaccination and the definition of the unvaccinated comparison group. Researchers may need to conduct sensitivity analyses, use negative-control outcomes, examine short intervals after vaccination and account for healthcare-seeking behavior. Analyses that compare people with similar recent health histories, or that use methods designed for time-varying confounding, can help determine whether an observed association is likely to represent a genuine vaccine effect.

The study does not undermine the value of COVID-19 vaccination for older adults; rather, it highlights the methodological care required to measure that value accurately. For clinicians, policymakers and the public, the message is that real-world vaccine evidence is strongest when biological protection is evaluated alongside the circumstances that determine who gets vaccinated and when. As SARS-CoV-2 continues to evolve and vaccine formulations are periodically updated, understanding the healthy vaccinee effect will remain essential for distinguishing the protection delivered by immunization from the protection that appears because healthier people are more likely to receive it.

Subject of Research: Healthy vaccinee effect and the evaluation of updated COVID-19 vaccines in elderly populations.

Article Title: Healthy vaccinee effect in the evaluation of updated COVID-19 vaccines in elderly populations.

Article References:

Lyth, J., Spreco, A., Hinkula, J. et al. Healthy vaccinee effect in the evaluation of updated COVID-19 vaccines in elderly populations. Nat Commun 17, 8014 (2026). https://doi.org/10.1038/s41467-026-76312-x

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41467-026-76312-x

Keywords: COVID-19 vaccines, updated vaccines, SARS-CoV-2, elderly populations, healthy vaccinee effect, vaccine effectiveness, epidemiology, observational studies, confounding, public health.

Ebola vaccine research has taken a step toward broader protection against one of the most persistent challenges in filovirus medicine: the existence of multiple Ebola virus species that can cause severe human disease. In a study published in Nature Communications, Weidle, Brunette, Wrenn and colleagues report that a pan-Ebolavirus nanoparticle vaccine protected rodents from lethal infection with both Zaire ebolavirus and Sudan ebolavirus. The finding is significant because vaccines designed around a single viral species may not provide reliable protection against genetically distinct Ebola viruses, particularly those responsible for separate outbreaks in different regions of Africa.

Ebola viruses belong to the filovirus family, a group of filament-shaped, enveloped viruses capable of causing hemorrhagic fever. Zaire ebolavirus is the species most closely associated with the large West African epidemic of 2014–2016 and remains the primary target of licensed Ebola vaccines. Sudan ebolavirus, however, is sufficiently different at the molecular level to present a separate immunological challenge. Outbreaks caused by Sudan virus have repeatedly demonstrated the need for countermeasures that are not limited to one viral lineage. A vaccine capable of recognizing shared features across several Ebola viruses could therefore simplify outbreak preparedness and improve the speed of emergency responses.

The strategy described in the study is based on nanoparticle vaccine technology. Nanoparticles can be engineered to present viral antigens in a highly organized, repetitive arrangement that resembles the dense surface of an actual virus. This geometry can improve the activation of B cells, the immune cells responsible for producing antibodies, by efficiently cross-linking B-cell receptors. Nanoparticles may also enhance the delivery of antigens to lymphoid tissues, where immune responses are initiated and refined. Rather than presenting a soluble protein in a relatively dispersed form, the platform is designed to display Ebola-related molecular targets in a configuration that can stimulate a stronger and more coordinated response.

A central challenge in creating a pan-Ebolavirus vaccine is selecting antigens that are both accessible to the immune system and sufficiently conserved among viral species. Ebola viruses share a broad structural organization, but their surface glycoproteins contain regions that vary in sequence and shape. The glycoprotein is especially important because it enables the virus to attach to host cells and enter them. Antibodies that bind to vulnerable regions of this protein can block infection, interfere with membrane fusion or mark viral particles for destruction by immune cells. A broadly protective vaccine must therefore encourage immunity against sites that remain functionally important even as the virus evolves.

In the rodent experiments, the vaccine was evaluated against lethal challenge with viruses representing the Zaire and Sudan species. Such challenge studies are designed to test whether vaccination-induced immunity can prevent severe disease after exposure to a high-risk pathogen. Protection in this setting reflects the combined activity of several immune mechanisms, including neutralizing antibodies, antibody-dependent cellular functions and virus-specific T-cell responses. Antibodies can prevent viral entry into cells, while T cells and other immune components help eliminate infected cells and limit the spread of infection. The reported protection across both virus species indicates that the nanoparticle formulation generated immune recognition broad enough to cross an important species barrier.

The result does not mean that the viruses are identical, nor does it establish that the vaccine will perform in humans in the same way. Rodent immune systems, dosing schedules and routes of exposure can differ substantially from human conditions. Animal challenge models are nevertheless a crucial stage in vaccine development because they reveal whether an immune response is capable of controlling infection under stringent circumstances. They also allow researchers to examine how quickly protection develops, how long it persists and whether vaccination reduces viral replication and tissue damage. Further studies will be needed to determine which immune markers best predict protection and whether the platform can be adapted for use against additional Ebola species.

The broad scope of the vaccine could have practical implications for epidemic preparedness. Existing Ebola vaccination strategies have demonstrated that immunization can protect against severe disease, but the need to match a vaccine to a particular viral species can complicate decisions during an outbreak. When the causative virus is initially unknown, health authorities may face uncertainty over which product to deploy. A pan-Ebolavirus formulation could potentially reduce that uncertainty by providing coverage against more than one major pathogen. It could also be useful for laboratory personnel, health-care workers and communities living in regions where different Ebola species may emerge over time.

Nanoparticle approaches may offer additional advantages beyond breadth. Their modular design can allow scientists to alter the antigen displayed on the particle without rebuilding the entire vaccine concept from the beginning. This flexibility is relevant to viral pathogens, which can change through mutation and may contain several related species with distinct antigenic profiles. At the same time, the platform must meet demanding standards for manufacturing consistency, stability, storage and safety. A formulation that performs well in laboratory animals must eventually demonstrate reproducible production, acceptable tolerability and durable protection in progressively more advanced models before clinical testing can be considered.

The study’s findings place nanoparticle engineering among the most promising strategies for developing next-generation filovirus vaccines. By combining multivalent antigen presentation with targets shared across Zaire and Sudan viruses, the researchers have demonstrated a route toward broader Ebola protection in rodents. The work does not eliminate the need for species-specific vaccines or replace surveillance, rapid diagnostics and infection-control measures. It does, however, provide experimental evidence that a single vaccine design can generate protective immunity against two medically important Ebola viruses. As outbreaks continue to expose gaps in preparedness, such cross-species technologies could become an important part of the scientific effort to prevent Ebola from turning a local emergence into a global health crisis.

Subject of Research: Pan-Ebolavirus nanoparticle vaccine protection against lethal Zaire and Sudan virus infection in rodents

Article Title: Pan-Ebolavirus nanoparticle vaccine provides protection in rodents from lethal infection by Zaire and Sudan viruses

Article References: Weidle, C., Brunette, N., Wrenn, S.P. et al. Pan-Ebolavirus nanoparticle vaccine provides protection in rodents from lethal infection by Zaire and Sudan viruses. Nature Communications (2026). https://doi.org/10.1038/s41467-026-76114-1

Image Credits: AI Generated

DOI: 10.1038/s41467-026-76114-1

Keywords: Ebola virus, Zaire ebolavirus, Sudan ebolavirus, pan-Ebolavirus vaccine, nanoparticle vaccine, filoviruses, viral immunology, infectious disease, vaccine research, rodent models

Exclusive: anonymous flagging service says cases have surged, as watchdog says AI is making sexualised or ‘nudified’ content easier to produce

Children in the UK have reported a surge in explicit deepfake images featuring their likenesses, as a safety watchdog warned AI is making such content easier to produce.

The Report Remove service, which blocks intimate images from appearing online, said there had been a rapid increase in imagery that had been digitally manipulated or “faked” in some way, including with AI and nudification tools.

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© Photograph: Peter Dazeley/Getty Images

© Photograph: Peter Dazeley/Getty Images

© Photograph: Peter Dazeley/Getty Images

The penalty, imposed by a state judge, is on top of a $375 million fine ordered by a jury that found Meta misled users about the safety of its platforms.

Apple has filed a legal complaint with the UK’s Investigatory Powers Tribunal seeking to overturn a secret government order requiring the company to enable access to encrypted customer data stored in its cloud services.The challenge, reported in early March 2025, targets a technical capability notice (TCN) issued by the Home Office in January under the Investigatory Powers Act 2016. The notice reportedly directed Apple to create the technical means for UK law enforcement and intelligence agencies to access data protected by the company’s Advanced Data Protection (ADP) feature: an optional end-to-end encryption layer for iCloud backups, photos, notes and other files that even Apple itself cannot normally decrypt, according to Financial Times.

Apple responded by withdrawing ADP for UK users rather than comply, stating that it would not build a “back door” or master key into its products or services. The company has long argued that creating such access points would undermine security for all users and could be exploited by malicious actors. Standard iCloud encryption remains available and is accessible to Apple when presented with a valid legal warrant, but ADP provides a higher level of protection that the firm says it cannot and will not weaken.

The case is understood to be the first major legal test of the Investigatory Powers Act’s provisions allowing authorities to compel technology companies to maintain capabilities to access encrypted material. The tribunal, an independent body that reviews complaints against the UK’s security and intelligence agencies, could quash the notice if it finds the order unlawful. Proceedings were expected to begin relatively quickly, though the government was anticipated to seek restrictions on public disclosure on national security grounds.

The dispute highlights the long-running tension between tech firms’ commitment to strong encryption and governments’ desire for lawful access in cases involving terrorism, serious crime or national security. Privacy advocates have warned that any mandated vulnerability in widely used systems could have global repercussions, while UK authorities maintain that such powers are essential for public safety and are subject to legal safeguards.Apple has consistently maintained that it has never built backdoors into its systems and will not do so. The outcome of the tribunal challenge could set an important precedent for how encryption and government surveillance powers interact under UK law.

MacDailyNews Take: We’ve been fairly clear on this subject for many years:

It’s not enough that every Brit alive has a government camera shoved up their ass 24/7/365? The UK has already slipped far down the slope that they ought to rename the place Airstrip One. – MacDailyNews, November 3, 2015

Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety. – Benjamin Franklin

The current batshit insane “leadership” of Airstrip One is having yet another crisis of confidence. – MacDailyNews, February 7, 2025

Censorship reflects a society’s lack of confidence in itself. – Potter Stewart

MacDailyNews Note: Apple’s Advanced Data Protection for iCloud is an optional setting that offers Apple’s highest level of cloud data security. If you choose to enable Advanced Data Protection, the majority of your iCloud data — including iCloud Backup, Photos, Notes, and more — is protected using end-to-end encryption. No one else can access your end-to-end encrypted data, not even Apple, and this data remains secure even in the case of a data breach in the cloud.

How to turn on Advanced Data Protection for iCloud

On Mac

1. Choose Apple menu  > System Settings.
2. Click your name, then click iCloud.
3. Click Advanced Data Protection, then click Turn On.
4. Follow the onscreen instructions to review your recovery methods and enable Advanced Data Protection.

On iPhone and iPad

1. Open the Settings app.
2. Tap your name, then tap iCloud.
3. Scroll down, tap Advanced Data Protection, then tap Turn on Advanced Data Protection.
4. Follow the onscreen instructions to review your recovery methods and enable Advanced Data Protection.

More info about Apple’s Advanced Data Protection for iCloud here.

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