Only Fatal to Adults

So the Depopulation Bomb has dropped, usually in the form of a highly selective virus or bacteria that is only fatal for adults, leaving the kids to inherit the world. Frequently seen in After the End fictions, Only Fatal to Adults has two variations: In the first, death strikes at the onset of puberty, killing only the sexually mature. In the second, the highly selective agent of the Depopulation Bomb kills in the late teens or in early adulthood, killing only the socially mature.

Another important distinction is whether the Depopulation Bomb is only a concern that one time, or if it will begin to affect the kids when they grow up.

Due to the difficulty in convincingly presenting a hypothetical weapon with such specific depopulation capabilities (especially if in the second form, where the bomb seems able to detect a set of legal and social traditions that are only very loosely connected to biological changes), a popular form of this is to have a non-discriminating apocalypse wipe out mankind in general, then re-populate the planet, say, sixteen years later, with a bunch of infants who were locked away in a survival shelter at the time.

If the Depopulation Bomb is Only Fatal to Adults, then this trope justifies Parental Abandonment. It also justifies storylines in which children and teens have to take on the responsibilities of adults, or form extended families of their own in order to survive. Can also justify Teens Are Monsters if teens survive and are left to fend for themselves. In some variations, due to the ages of the characters and the intended audience, guns are rare and the Nerf Arm is ubiquitous. Sometimes, there are even lasers.

This will pretty much always lead to a Teenage Wasteland. Compare Gendercide. Also see Infant Immortality.

Comic Books

 * The DCU miniseries World Without Grownups had all the adults spontaneously disappear from the face of the earth. Robin, Superboy, and Impulse had to get everything together if humanity was to be saved, leading directly to their formation of Young Justice.
 * Natually, the DCAU provided its own spin in the Justice League Unlimited episode "Kid Stuff", where Mordred banishes all the adults from Earth, and Superman, Batman, Wonder Woman, and Green Lantern have to get turned into preteens to go back and stop him.
 * In the Pre-Crisis Earth-1 Superman continuity, Superman's adoptive parents, Jonathan and Martha Kent, died after contracting a virus that only affected adults. Superman was still Superboy at the time, so the virus did not affect him. Several years later, Lois Lane and Lana Lang contract the same virus and almost die before the now adult Superman realizes that the virus entered his body as well, and his body created anti-bodies to counteract it.
 * "Kids Rule OK", a strip in 70's British comic Action. The vast majority of adults die, leaving only rampaging gangs of kids that start to beat seven kinds of crap out of each other. Until the comic fell foul of Moral Guardians and they all make peace after being given a Stern Talking To.
 * One Hellblazer mini-arc features John Constantine's niece being enlisted to travel to an island where a group of Vampire Children all under the age of 13 who attack any adults that come near the island, but don't harm other children.

Fan Fiction

 * This kind of thing seems to happen once a week in the universe of premier Mary Sue Marissa Picard, where Stephen Ratliff uses this kind of stuff to justify regularly allowing his Kids Crew protagonists to have command of starships, starbases, entire systems, etc.... One story in particular had a group of hijackers use a sleeping gas that only affected adults for no apparent reason beyond this.
 * Eiga Sentai Scanranger had a Monster of the Week armed with poison that dehydrates anyone who touches it/drinks it, but only if they're over 25. It's unclear why that was brought up when what wasn't brought up was what the villains hoped to accomplish. The poison would only work on one of the six rangers, for crying out loud.
 * In Day of the Barney everyone over the age of thirteen disappears. And by "disappears", I mean Barney brainwashes all the younger children to slaughter them en masse before joining their purple friend in happy fun-fun time forever. And when they reach the age of thirten, they get to go on a vacation...

Films -- Live-Action

 * The 1972 cult film Gas-s-s-s, where an industrial accident releases a poison gas that kills everyone on earth over the age of 25. In the rest of the film, the main characters have to learn to survive on their own. The concept is laden with Fridge Logic: the gas was designed for use in The Vietnam War, but the average age of a soldier in 'Nam was 19.
 * Inverted in Clive Barker's The Plague, in which every child on Earth under the age of nine suddenly falls into a coma, and every baby born in the next ten years is also born comatose.

Literature

 * In the novel Worlds Apart by Joe Haldeman, Earth has been devastated by the second type. He ties the disease to when the body reduces production of human growth hormone. So there are some adults around because they suffer from acromegaly, a disease where adults produce too much human growth hormone.
 * This was the premise for Shade's Children by Garth Nix. Except here the world is run by evil overlords who chop up anyone over 14 for body parts. When they took over, though, everyone over 14 instantly disappeared and beyond this being the fault of the overlords it's never completely explained.
 * In The Subtle Knife, the second book of the His Dark Materials trilogy, there's a world in which there are soul-eating 'spectres' that only target adults. At one point the heroes are in a city only occupied by children, although it turns out that most of the adults left, rather than being caught by the spectres, and will return once the spectres move on.
 * The plot of the Blake and Mortimer book The Voronov Plot revolved around a virus recovered by a KGB scientist from a crashed Soviet satellite which was only lethal to adults. The scientist, Dr. Voronov, a Stalin admirer, planned to use the virus to overthrow the Soviet Union and conquer the West. Late in the book, he starts using the virus in a particularly despicable fashion:
 * The children's book The Girl Who Owned a City. The set 'death age' here was twelve, and most of the adults knew about it before they died.
 * This is most of the plot of The Fire-us Trilogy. A band of young children are living on their own, but eventually find a group of religious zealots who go so far as to name themselves after various religious passages.
 * The kids also find a group of elderly women in a retirement home, that survived only because post-menopausal women were the only adults that weren't affected by the virus.
 * An interesting variation: In Larry Niven's A World Out Of Time, only pre-adolescents can use the immortality treatment and cease aging, while those who pass puberty become immune to the treatment and age and die normally. Rediscovering an immortality treatment usable by adults and breaking the status quo of the immortal children's hegemony forms a large part of the book's second half.
 * In David Weber's Honor Harrington, people can get a treatment that will double or triple their lifespans, but only while they're still young. There are three levels of effectiveness. First generation Prolong can be performed as late as 25. Second generation treatment is only effective into the early teens, but gains a century or so more; Third generation, it is implied, will extend life even more effectively (it's very new, so the first people to get it haven't grown old yet), but requires genetic manipulation even before the recipient's birth..
 * Availability of Prolong is the single biggest quality of life difference between various worlds. For instance, it becomes a plot point that the Kingdom of Manticore is welcomed in an area they annex simply because Prolong had not previously been available there, save to the very rich, but the Manticoran public health system guarantees it to all.
 * The post-apocalyptic young adult novel series Countdown began with the release of a deadly virus that somehow turned everyone but young adults into black goo.
 * Inverted in the Left Behind series - in addition to righteous people in general, all children under an unspecified age are Caught Up in the Rapture. Presumably this would be justified by means of Children Are Innocent.
 * Except that any denomination that believes in the original sin sees babies as inherently sinful.
 * Except that many denominations that believe in original sin also believe in the Age of Accountability, which denotes that age at which a person becomes mature enough to be held responsible by God for his or her sins.
 * The premise of the book series Gone (novel). All people over the age of 15 disappear one day, and continue to disappear throughout the book, i.e once one turns 15, they vanish.
 * Only Fatal to Adults is combined with Gendercide in the backstory to George R. R. Martin's first novel Dying of the Light. Part of what has shaped the Kavalan culture is a biological weapon that kills any sexually mature woman.
 * In the novel Idlewild by Nick Sagan (Carl Sagan's son)
 * In Lord of the Flies the plane crash in the beginning kills all of the adults on board leaving the children to fend for themselves.
 * In Chris Adrian's book The Children's Hospital, all the adults  die of the strange dust disease;
 * The Reapers trilogy by Andrew Butcher relies on this trope: everyone over 18 dies of the mysterious Sickness, leaving the protagonists to fend for themselves. It turns out
 * Donaya Haymond's Waking Echoes has The Famine Fever, which is Only Fatal To Adults And Children, sparing the adolescents alone.
 * The Gentleman Bastard series has Black Whisper, a plague that typically gives anyone who hasn't entered puberty a case of the sniffles and everyone who's entered or completed it a case of screaming death. An outbreak in one particular district is what makes protagonist Locke Lamora an orphan at a young age.
 * Lauren Destefano's in-the-works series The Chemical Garden deals with genetically modified persons. The women all die at age twenty, and the men all die at age twenty-five.
 * The Young Adult novel Starters, by Lissa Price, is set in a post-war Dystopia where only the very old and the very young survive. The young can temporarily 'rent out' their bodies so the elderly can enjoy a virtual youth.
 * The Young Adult novel Starters, by Lissa Price, is set in a post-war Dystopia where only the very old and the very young survive. The young can temporarily 'rent out' their bodies so the elderly can enjoy a virtual youth.

Live-Action TV

 * Star Trek the Original Series had a planet that was an exact duplicate of Earth (amazing!) in the episode "Miri", on which the only survivors of a mysterious plague were a band of savage children. Their childhoods lasted centuries, but they were doomed to die at the onset of puberty.
 * The Star Trek Deep Space Nine episode "Quickening" features a planet where everybody is struck with plague that is present from birth, but usually only kicks off in adult age, killing the victim. This is then turned Up to Eleven when Bashir cannot cure the plague, but procures a prenatal vaccine (every baby whose mother received it through pregnancy will be plague-free).
 * The TV series Jeremiah took place fifteen years after a plague wiped out the current population of adults.
 * The Kiwi teen soap The Tribe has this as its backstory: a mysterious virus kills basically everyone over 18 or 21 and the kids and teens are left to fend for themselves. The show was half teen soap and half Cozy Catastrophe, and there were even lasers with stun settings. All it was missing was that A Clockwork Orange element of graphic, violent, badassness to make it realistic and gritty, but it tried.
 * Still, there was that heartwrenching intro...
 * "Authorities are appealing for calm throughout the evacuation process..."
 * The Stargate Atlantis episode "Childhood's End" (unrelated to the Arthur C. Clarke novel) involved a village where everyone committed ritual suicide after reaching a certain age, because they thought it was required to protect them from the Wraith. In truth, the Ancients set up an EMP field that incapacitated any technology straying into it and if the population grows too large, they will leave the field and get culled. Hence the suicides.
 * This is apparently the background story for Mystery Science Theater 3000 veteran City Limits, set in a post-apocalyptic Teenage Wasteland. James Earl Jones escaped the effect because, well, James Earl Jones!
 * Japanese TV series Bokura No Yuuki, is a Lord of the Flies reminiscent story of the latter case, where a microbe kills anyone 20 and older. They fortunately came up with convincing enough sounding Applied Phlebotinum to justify it.
 * The world of 2030 CE is plagued with Progressive Aging Syndrome, a disease that causes rapid aging and eventually death by a person's 30th Birthday.
 * An episode of Andromeda centered around a Lost Colony of Commonwealth children, who, due to years Voltarium exposure would cause them to die by adulthood. It's not so much only fatal to adults so much as 20 years of radiation exposure with no radiation treatments kills you.

Tabletop Games

 * The Carbon Plague in Cybergeneration uses this trope. At first, everyone who catches it dies. First kids start surviving it, then adults do. Some of the kids that survive it come out a little different. It's much less of a Depopulation Bomb than other instances of the trope. The death toll is around 5% of the world's population. Possibly a subversion: fear over the Carbon Plague allows the U.S. Mega Corps to found the Incorporated States of America and children are now demonized and feared with less political power or autonomy than before. Of course, the ability to turn your arms into guns might be a relevant tradeoff there.
 * In Tabletop RPG Bliss Stage, the Bliss only affects humans who are eighteen years or older. This means that everyone under eighteen is safe, but only until their eighteenth birthday...
 * The Dark Eldar in Warhammer 40000 got started when the birth of a new Chaos God turned out like this. Mix with Teens Are Monsters and serve for ten thousand horrifying years.
 * The Vitusdance in Engel killed off every adult in the world. And it happened more than once. No wonder that centuries from now Earth has managed to rebuild itself into a feudal level society.
 * Non-plague example: In the domain of Odaire in Ravenloft, the living puppet Maligno murdered all the adults except his creator, leaving the children to fend for themselves.
 * The Plague in KidWorld only kills adults or, failing that, renders them blind. Everyone in the world still carries it though, so the eyesight of a teenager will get progressively worse as he/she grows up until it is lost altogether.

Videogames

 * At the beginning of Yoshi's Story. Baby Bowser transforms Yoshi's Island into a figure book, and all the Yoshis become zombie-like (not dangerous, just zoned out and miserable). The only ones that weren't affected were a couple of Yoshi eggs that later hatched and took on Baby Bowser.
 * Inverted in Advance Wars: Days of Ruin. The Creeper only infects people under the age of 20/21...
 * In Final Fantasy VI, Kefka's death ray has claimed everyone over 18 in Mobliz. There is no evidence that any children died with them.
 * Not really explained either. Seems the kids only made it by chance, really...
 * Actually this is Nightmare Fridge Brilliance. Think about it...he intentionally killed all the adults in front of the children, and left them alive to grieve. He did it to make children cry.
 * Any question of Kefka's motives boil down to: 1) He's nuts or 2) he felt like it.
 * Wasn't there mention of the parents dying to save the kids?
 * A somewhat more indirect version explains the existence of Little Lamplight in Fallout 3. The kids were on a field trip when the bombs fell, the adults all died searching the wastes, and the Vault 87 dwellers wouldn't let the kids in  The kids' distaste for adults became tradition; any Lamplighter who turns 16 gets forced out and sent across the Wastes to "Big Town", which considering the state of the place   is effectively this trope.
 * Reading some of those diary entries, it was hard not to see something a bit more sinister in the way those kids were treated.
 * The design document for Vault 29 in the canceled Van Buren plays in this trope---families were selected for the Vault, but everyone older than 15 was either turned away or redirected to another Vault in the chaos. A sentient supercomputer was to raise the kids.

Webcomics

 * In Tales of the Questor, an ancient elf king wished for eternal youth for his people. He got it: Elves now die around age 20 ("Just old enough to make more elves") - which more or less caused the collapse of their society and left the surviors living as thieves and scavengers.
 * Also, there have been references to "the Crimson Plague" or "the Scarlet Plague," which according to Word of God decimated the Racconan population on at least two occasions, killing the very old and very young--- the main reason that, despite being a long-lived race, the current population of Antillia has very few extremely old Racconans, and very few families with multiple children....

Web Originals

 * Lost Boys of the Cascades is a web-published story about children struggling to survive after a pandemic killed all the adults.

Western Animation

 * A Lighter and Softer variation happens in Lloyd in Space, where a space cloud merely paralyses adults rather than kills them, while kids and teens are unaffected.
 * Played With on Young Justice: five powerful magic users cast a spell that makes every adult on the planet disappear. However, halfway through the episode it's revealed that they actually split the world in two dimensions—from the adults' perspective, every child in the world under 18 just vanished. Meanwhile Captain Marvel, who can switch from a kid to an adult, shifts between worlds when he transforms, coordinating the effort to fuse the worlds back into one.
 * It actually takes idealistic and cynical approaches to such an event. The kids' dimension is portrayed as fairly stable, with the older kids looking after the younger ones and waiting patiently for the heroes to save the day. The adults' dimension suffers widespread rioting and panic, though some of this was made worse by the Light's interference.

Real Life

 * Many common childhood illnesses can be quite serious if caught as adults, and could lead to severe complications for the fetus if caught while pregnant.
 * The Varicella zoster virus (aka Chicken pox), while mostly harmless to children, can be fatal if contracted in adulthood, which is why parents often try to get their children infected while they're still young so they can develop immunity. Since there are still minor risks in childhood (approximately the same risks one would have from a case of the flu, plus the obvious danger of passing on the virus to a non-immune adult), the recent development of a vaccine has been quite welcome. And if that's not enough, even if you get it as a child it can turn up again when you're adult in the much more uncomfortable form of Herpes Zoster (shingles).
 * The same reasoning (and infection attempts) are often applied to Rubella (aka German measles), at least for young girls. In children, it's unpleasant but mostly harmless - in pregnant women, it is extremely serious, able to blind or kill the fetus.
 * Mumps, while not usually fatal, is much more unpleasant to adults than children. It's actually known to sometimes cause sterility in adult men due to severe inflammation and swelling of the testes.
 * Most in-house pesticides work in this manner, killing only the adult insects. A second "bug bomb" is set off a week or so later to get any that were still in eggs.
 * Huntington's chorea only becomes noticeable in adulthood (the exact age varies, but it often only manifests after the carrier has had children).