Attenuated vaccines introduce a weakened version of the virus into the body

Breaking down the different types of vaccine technologies

There are several different types of vaccines. Each type is designed to teach your immune system how to fight off germs—and the serious diseases they cause. This short overview breaks down the differences between the types.

The oral, live virus vaccine is the most robust but carries more risks

The live virus vaccine, delivered via oral drops, induces the best protection in the body. Because it includes a live, weakened form of the virus there's an extremely small risk it can sicken recipients and potentially cause paralysis. Recipients also shed the virus in their stool, which can rarely lead to vaccine-derived cases of the virus if the virus mutates. (Some users may experience a paywall.)

What are universal vaccines?

As viruses mutate and develop, vaccines have to adapt, leading to regular recommended injections like flu shots. Researchers are working to develop universal vaccines that aim to protect against multiple virus variants if not entire virus families. These vaccines work by creating broadly neutralizing antibodies (bnAbs) that target aspects of viruses that don't typically mutate and are integral to the virus' survival.

How do vaccines work? Watch this brief 101

Watch this under-3-minute video explaining how vaccines use the body's immune system to prepare our bodies against viral and bacterial threats to our health.

Before vaccines, there was 'variolation': what was it?

Before the technology behind vaccinations was discovered, some keen observers of medicine around the globe noticed how previous infections could impact future ones. Learn about the techniques early physicians used before they had vaccines.

Understanding vaccine side effects

A vaccine is a medical intervention, and as with any medical intervention, may have side effects. This article discusses side effects and adverse events related to vaccination.

Measles infection can cause long-term immune system “amnesia”

The measles virus attacks the body's immune system, including preying on T and B cells in the lymphatic system. These cells hold memories of past infections, which can be degraded as the virus destroys them. This leaves patients susceptible to other infections for a year or longer.

Small genetic changes force flu vaccines to be updated regularly

Through a process called antigenic drift, influenza viruses accumulate tiny copying mistakes in their genes. These gradual changes alter the virus enough that immunity fades, making updated vaccines necessary each flu season.

A technical look at the measles virus and its life cycle

The measles virus is made up of a single strand of RNA, packaged inside an envelope that varies in shape and size. A negative-sense paramyxovirus—the same family as mumps—the virus is encased in proteins that help it attach to immune cells inside the body.

The measles vaccine has saved an estimated 94 million lives since its introduction

Measles killed an estimated 2.6 million people globally in 1980, after the development of a vaccine but before its widespread dissemination. By 2014, that figure had dropped to an estimated 73,000.

Malaria vaccines are not routine because they have limited effectiveness

Both of the currently recommended malaria vaccines have limited effectiveness, require multiple doses, and provide protection for only a short period of time. One, approved by the World Health Organization in 2021, is only about 30% effective, requires four doses, and protection fades within months. The other requires three shots, and some research indicates it is 75% effective for a year.

Herd immunity works by slowing down viral transmission until it dies out

Herd immunity refers to a population whose vaccination rates against a given virus are high enough that transmission dies out before the bug can find the next unvaccinated person to infect. Rates needed to achieve this depend on how contagious a virus is. This video gives a quick visual explanation of how it works.

Wastewater testing has detected genetic evidence of polio, triggering vaccine boosters

Sampling of wastewater in London in 2022 detected fragments of polio virus, suggesting a vaccine-derived version of polio may be circulating. No one became ill, but the finding did trigger calls for a renewed booster inoculation campaign.

How mRNA vaccines work

mRNA COVID-19 vaccines were developed faster than any vaccine ever made. Even more enticing, the underlying technology may unlock preventive treatments for a wide-range of diseases.

Learn how monoclonal antibodies, which mimic the body's antibodies, can fight diseases like Ebola

Monoclonal Antibodies mimic the antibodies produced naturally by the immune system. These molecules target specific parts of the virus, preventing them from entering cells or interfering with their ability to cause harm or infection.

A vaccine against Epstein-Barr virus, researchers hypothesize, could potentially prevent MS

As many as a quarter of MS patients have antibodies in their blood that bind to both a central protein in Epstein-Barr virus and a protein made in the brain and spinal cord that—when attacked—leads to a breakdown of protective nerve fiber insulation. This suggests the immune system's primed to attack the nervous system after mounting a defense against Epstein-Barr.

Fevers are an immune response to create hurdles for pathogens

Substances called pyrogens prompt the brain to raise the body temperature to levels where bacteria and viruses struggle to survive. The higher temps also support immune cells fighting off the invaders.

Environmental conditions, shifting immunity, and viral strain could help explain 2025 spike

The surge in HFMD in the summer and early fall of 2025 in the mid-Atlantic could be the result of a confluence of factors, including a more virulent strain of disease-causing virus, good environmental conditions for the virus to spread—hot, humd—and a potential immunity gap among kids due to milder HFMD outbreaks the previous year.

An Ebola vaccine was developed during the 2018 west African Ebola outbreak, but the 2026 Ebola outbreak is with a different species of the virus, not the one that the vaccine is approved to treat.

Learn how monoclonal antibodies, which mimic the body's antibodies, can fight diseases like Ebola.

Women typically have more robust immune responses than men

This difference helps women better combat infectious diseases, but this more turbo-charged response may also make women more vulnerable to autoimmune diseases by potentially priming their immune systems to overreact to their own cells and tissues and label them as invaders that must be destroyed. Roughly 80% of American women have autoimmune conditions.

Wolbachia is a naturally occurring bacterium being employed to fight dengue

Scientists are fighting dengue spread in a roundabout way: injecting bacteria into Aedes aegypti mosquito eggs, which blocks the dengue virus from replicating in the tissue of mosquitoes. Researchers hope the bacterium will be passed to future generations, inoculating them against dengue. Wolbachia is also being investigated to combat other mosquito-borne diseases.

On average, people smell worse if they're sick

For a small 2014 research study, a panel was tasked with sniffing the smelly t-shirts of people who had been injected with a compound known to activate the immune system and those of controls without the shot. It found that those who were acting as if unwell (due to the injection) generally smelled worse. Subsequent work found that those who sniffed unpleasant odors had a mild immune response of their own—perhaps to protect them from disease. (Some users may experience a paywall.)

Genetically modified viruses can help construct battery electrodes

MIT scientists' modifications caused the viruses to attract conductive materials, such as gold ions, which the viruses self-assembled into nanowires that could be used in batteries. These components allow batteries to be thinner and flexible enough to be constructed into new shapes.

An explanation of the weak nuclear force, which can induce some forms of radioactive decay

While the strong nuclear force holds the protons and neutrons together in an atomic nucleus, despite the electromagnetic force pushing protons apart, the weak nuclear force can change the identity, or flavor, of the quarks that make up these particles. In doing so, protons can be converted into neutrons, and vice versa, altering the stability of atomic nuclei.

Most cases of West Nile virus are asymptomatic in people

About 1 in 5 infected people develop symptoms from West Nile, including symptoms such as fatigue, head and body aches, and vomiting. But around 1% of patients develop severe complications such as encephalitis or meningitis, which can be life-threatening. Those who are most likely to become severely ill are people over age 60.

Indirect prompt injection is a major security flaw of generative AI systems

These attacks can manipulate AI behavior by hiding instructions in websites and PDFs that become part of training data. The more companies connect sites, services, and sensitive datasets to AI tools, the greater the chances of exposure to malicious code.

Experimental hantavirus vaccines and therapies, still under development, have long been funded by the US military.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

Doctors differentiate between a phobia and fear by asking patients whether their fear interferes with their day-to-day activities.

Tattoos remain visible on your skin thanks to immune cells called macrophages

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Poison ivy's rash-causing compound is found in the plant's roots, stem, and leaves—so coming into contact with any part of the plant can lead to rashes for the 85% of people who are allergic to it.

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

After 25 people used virtual reality headsets to practice flying with virtual wings—flapping their arms—their visual cortex responded to the wings almost as if they were real arms, treating them as body parts.

Elk Cloner, the first computer virus to spread in public, was written as a practical joke by Richard Skrenta, a Pittsburgh high school student.

Listen to an in-depth conversation on the links between Parkinson's disease and herbicide exposure and the challenging pace of scientific investigation.

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

'Silent' fireworks have gained more interest in recent years as a quieter celebratory option.

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

The power and influence of the American presidency have expanded significantly over time—far beyond what the founders envisioned.