Health
How Much Vaccination Stops a Measles Outbreak?
To stop the spread of an infectious disease like measles, you don’t have to vaccinate everyone. But you do have to vaccinate many.
Just how many? To let you discover for yourself, we simulated an outbreak of a hypothetical disease, about as contagious as the flu. (A lot less contagious than measles.)
We’d like you to contain it. But first, some basics:
Here’s a sick person in a population with no protection against the disease.
That person infects some neighbors.
Who, in turn, do the same.
Soon, almost everyone has been infected.
In a world where no one has immunity, infectious diseases spread exponentially. That’s what happened early in the Covid pandemic.
But for most infectious diseases, many people will already have some level of immunity — whether through a previous infection or through vaccination — and this can slow the spread.
Now it’s your turn to try.
Level 1: Less Contagious
How low can you set the vaccination rate to contain the outbreak?
This simulation uses randomness, so the results will turn out somewhat differently every time you play it. But there are patterns that you can discover: When the vaccination level is below around 40 percent, outbreaks are very likely. Above that level, they’re quickly extinguished.
Chance of an outbreak growing out of control for a less contagious disease
That sharp gradient from red to white shows us this “herd immunity” threshold, where vaccination can halt an outbreak and protect the unvaccinated. (Including those who can’t be vaccinated, such as infants and people with weakened immune systems.)
The difference is stark. A little below that threshold, outbreaks easily grow out of control. Above it, they are quickly squelched. This is why it’s so important to keep vaccination levels above the herd immunity threshold.
Next, let’s see what happens with a disease that’s more contagious.
Level 2: More Contagious
How low can you set the vaccination rate to contain the outbreak?
Because this disease is more contagious, it can more easily slip through the gaps of unvaccinated people.
That’s why the vaccination level needed for herd immunity rose from around 40 percent to around 60 percent in this example: It takes greater levels of vaccination to contain a more contagious infectious disease.
Chance of an outbreak growing out of control for a less contagious disease …
… and for a more contagious disease
So far, all our simulations have assumed that vaccination is evenly distributed. In reality, that isn’t the case.
Our final simulation tries to capture two neighboring communities. Think of them like two school districts in the same county. In one district, 75 percent of students are vaccinated. In the other, just 50 percent are.
That means the average vaccination rate for the county overall is 63 percent — right around the herd immunity threshold for our simulated disease. But see what happens.
Unvaccinated pockets
50% Vaccinated
75% Vaccinated
For the most part, the 75 percent district is protected, while the 50 percent district is overrun, even though they sit right next to each other. Herd immunity operates at a local level, and the average vaccination rate for a broad region can mask smaller communities at risk.
On a few tries, you might have gotten lucky and seen the outbreak fizzle out. This, too, mimics reality. But luck is not an effective public health strategy.
The simulated world you saw above mirrors a real-world problem: There are increasingly many parts of the U.S. where skepticism of vaccines has gained momentum and childhood vaccination rates have fallen.
And measles is far more contagious than the disease we simulated — because of space constraints, we could not even simulate it in this form. It’s so contagious that a vaccination rate of 50 percent or even 75 percent won’t contain an outbreak.
How contagious is measles?
Epidemiologists estimate the contagiousness of an infectious disease with a “basic reproductive number,” or R0 — how many people a sick person infects, in a community with no protection.
A disease can grow out of control if an infected person infects more than one other person, on average. A person with the flu can infect one to two others — an R0 between 1 and 2.
But a person with measles can infect 10 times as many:
Disease
Contagiousness (Est. R0)
Measles
Whooping cough
Covid (Omicron)
Chickenpox
Polio
Covid (Delta)
Flu (1918)
Seasonal flu
For measles, a 1982 study put its R0 between 12 and 18. A more recent review of studies found a very wide spread, with a median of around 15 in the Americas.
That means measles is one of the most contagious diseases known. And there’s a direct relationship between contagiousness and the level of protection needed for herd immunity.
Population protection needed for herd immunity
Reaching herd immunity means each infected person can infect only one other person or fewer, on average. That means, at the high end of the measles range, you’d need to prevent 17 of 18 infections, or over 94 percent. That’s why health officials set a goal of vaccinating 95 percent of people against measles.
(The measles vaccine, unlike vaccines for some other infectious diseases, is very effective and its protection lasts decades; measles also is extremely unlikely to develop mutations that allow it to evade the vaccine.)
The average vaccination rate for kindergartners in the U.S. has fallen below that threshold since the pandemic. Most kindergarteners now live in states where the vaccination rates are below herd immunity.
Number of states with kindergarten measles vaccination rates below 95 percent
Many kindergartners live in counties and go to schools where the rates have fallen even further, below 80 percent or even below half — making it possible for measles to spread like wildfire.
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No sex for the win? This was the advice given to this year’s NBA champions.
New York Knicks owner James Dolan addressed the now-champs as they headed into the playoffs in April 2026, acknowledging their high potential to eventually win the championship.
“I don’t know if you understand what it would mean for you to win a championship this year … It would be life-changing,” he said. “It will stick with you the rest of your lives, and if you don’t win, you’ll be thinking about it the rest of your lives.”
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As Dolan’s inspirational speech to the team went on, he explained how the next 10 weeks would require each player to make sacrifices – watching their diets, getting proper sleep and perhaps even abstaining from sex.
“You need sacrifice and you need to eliminate all the distractions around you,” he said.
Jalen Brunson of the New York Knicks celebrates with the Bill Russell NBA Finals Most Valuable Player Award trophy and Knicks owner James Dolan after defeating the San Antonio Spurs in Game Five of the 2026 NBA Finals at Frost Bank Center in San Antonio, Texas, on June 13, 2026. (Gregory Shamus/Getty Images)
“I had this idea that maybe you should give up sex for the next 10 weeks,” the owner said. “You don’t have to give up sex for the next 10 weeks – but, like the Spartans … They denied themselves, so that they can have an edge. Get the edge.”
This received a few snickers from the team, and Dolan responded, “Don’t tell [your wives and girlfriends] you’re not going to have sex and don’t tell them it was my idea. But let them know what this is going to be like … and how they’re going to have to sacrifice, too.”
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Dr. Anna Elton, licensed marriage and family therapist and clinical sexologist in Massachusetts, confirmed that this belief has been around for centuries, dating back to the ancients Spartans and early Olympic competitors.
Avoiding sex can preserve energy, increase aggression and sharpen focus, according to Elton.
The theory behind abstaining from sex for better athletic performance supports that it can preserve energy, increase aggression and sharpen focus. (iStock)
But modern research has found little evidence that consensual sexual activity negatively impacts strength, endurance, reaction time or athletic performance when it occurs at least 10 hours before competition, the doctor countered.
However, “activity very close to competition may affect recovery measures,” she added. What may be more important, according to Elton, is the psychological value of abstinence.
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“Choosing to abstain can reinforce discipline and total commitment to a larger goal,” she said. “In those cases, the advantage may come more from mindset and focus than from any physical effect.”
“Whether the sacrifice is alcohol, social activities, favorite foods or sex, the message is often the same: ‘We are all in.’”
New York Knicks guard Jalen Brunson celebrates with teammates after the Knicks defeated the San Antonio Spurs in game five of the 2026 NBA Finals at Frost Bank Center in San Antonio, Texas, on June 13, 2026. (Geoff Burke/Imagn Images)
The science of abstinence
This discussion has historically focused on men, which Elton said is often based on “misconceptions about testosterone and energy depletion.”
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“Research has not demonstrated that normal sexual activity causes a meaningful decline in athletic performance, and concerns about testosterone depletion have not been consistently supported by the evidence,” she said.
“For women, sexual activity may have additional benefits related to stress reduction, emotional regulation and relationship satisfaction.”
Abstaining from sex for athletic performance may create a sense of discipline, minimize distractions, maintain focus on training and reinforce a team culture centered on sacrifice and commitment, experts say. (iStock)
In a separate interview with Fox News Digital, Dr. Anthony Puopolo, a men’s health expert and lead medical provider for RexMD, echoed Elton’s assessment that research largely does not support abstinence as a performance enhancer.
This is despite a small amount of evidence that suggests engaging in sexual activity within two hours of competition could pose a risk to cardiovascular recovery.
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“Unfortunately, nearly all studies (99%) have been conducted in males aged 20 to 40, so there is virtually no data on female athletes, older athletes or diverse populations,” said the Puerto Rico-based expert. “We know what to tell the Knicks, but we are not sure what to recommend for the New York Liberty.”
Importance of connection
Elton said abstinence may still offer psychological benefits for some competitors. “For some athletes, it can become part of a pre-competition ritual that enhances confidence,” she told Fox News Digital.
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Some other potential benefits of sexual activity include stress reduction, improved sleep, mood enhancement, emotional connection with a partner and relief from performance-related tension.
“Strong, supportive relationships are associated with better psychological resilience, which can be valuable during high-pressure competitions,” Elton said.
“One of the most overlooked performance advantages may be having a supportive relationship waiting at home,” a doctor said. (iStock)
“Ultimately, there is no universal rule,” she went on. “What helps one athlete perform at their best may not help another.”
Elton stressed that sleep, recovery, nutrition, stress management and support from loved ones are universal performance boosters.
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“Athletes devote tremendous attention to training their bodies, while overlooking the importance of their personal relationships,” she cautioned. “A supportive partner can be one of the greatest assets during a demanding season.”
“If competition requires temporary sacrifices, make those decisions together and keep communication open.”
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Eliminating sugar from your diet may seem like the key to healthy eating, but research suggests it could have unintended effects on digestive health.
A study presented at ENDO 2026, the Endocrine Society’s annual meeting, suggests that a total lack of sucrose, or table sugar, may harm gut health and disrupt the body’s natural metabolism.
To explore how the total absence of dietary sugar impacts the body, researchers at the Dasman Diabetes Institute in Kuwait City conducted a 16-week study on two groups of mice. Both groups were placed on a low-fat diet, but with one critical difference.
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One group consumed a low-fat diet that included a standard amount of sucrose, while the other group ate a low-fat diet that was completely sugar-free, according to the study’s press release.
Throughout the trial, the scientists monitored a wide variety of physiological factors, including the animals’ weight, glucose tolerance, insulin sensitivity, hormone levels, internal inflammation and the specific composition of their gut bacteria.
A total lack of dietary sugar can cause imbalances in the gut bacteria and lead to signs of fatty liver disease, even without any weight gain, researchers said. (iStock)
The study outcome suggested that completely removing sugar caused several unexpected health problems.
“Completely removing sucrose from a low-fat diet may unexpectedly disrupt gut health and promote inflammation and metabolic dysfunction,” Rasheed Ahmad, principal scientist and head of the Immunology & Microbiology Department at the Dasman Diabetes Institute, said in the release.
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Even though the mice on the sugar-free diet did not gain any extra weight compared to the control group, their internal health indicators deteriorated.
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The animals that lacked sucrose developed an imbalance in their gut microbes and increased inflammation within the intestines and liver.
They also showed signs of poor glucose regulation, insulin resistance and cellular changes associated with fatty liver disease, according to the research.
Future dietary guidelines may shift away from strict, absolute sugar bans and instead focus on overall gut health through balanced nutrition. (iStock)
“The findings suggest that complete removal of sucrose from a low-fat diet may negatively affect gut microbiota and metabolic health,” Ahmad concluded.
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While the risks of high-sugar diets are well-established, the researchers noted that little attention has been given to the effects of completely eliminating sugar from low-fat meals.
Scientists say these new findings highlight that dietary carbohydrates play a valuable role in supporting balance between the immune system and the gut microbiome.
Completely cutting sucrose from a low-fat diet can unexpectedly trigger gut inflammation and disrupt the metabolism, experts say. (iStock)
Because this research was conducted on mice over a relatively short 16-week period, further clinical trials are necessary to determine whether a completely sugar-free diet causes the same gut and liver inflammation in humans.
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Additionally, the study focused specifically on removing sucrose from low-fat meals, meaning the results might not apply to people eliminating sugar while following higher-fat or ketogenic eating plans, the researchers noted.
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The team believes that future dietary guidelines may shift away from strict, absolute sugar restrictions and instead place a greater emphasis on maintaining a diverse, healthy population of gut bacteria through balanced nutrition.
“In the long term, these findings could help improve strategies for preventing and managing metabolic disorders, fatty liver disease and chronic inflammatory conditions,” Ahmad said.
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