Numerous individuals on the Island made use of a vaccine. It is unknown what disease, if any, the vaccine was ever meant to counteract. Characters often lied about its effects.


The vaccine was seen up close on at least two occasions in the series and appeared to be a yellow translucent liquid. The vials were both labeled "CR 4-81516-23 42." The vial seen at the Staff also contained the notation "RX-1 GND" and the station's logo on the label. The vaccine appeared to be administered in most cases via a jet injector - although it could also be given via a syringe. ("Man of Science, Man of Faith")  ("Maternity Leave")

It appeared that the vaccine was originally manufactured by the DHARMA Initiative, although the kit found on the pallet drop appeared to suggest some party was continuing to manufacture the vaccine after the time of the Purge.

The vial from the Staff, displaying the codes RX-1 GND and CR 4-81516-23 42.


As described by Kelvin, the vaccine was intended to combat some sort of sickness on the Island - although he never elaborated on the nature of the disease or its symptoms. Kelvin indicated that Desmond should give himself a shot of the vaccine every nine days - and that anyone going outside the station without protection (e.g. a HAZMAT suit) would be at risk of contracting it. Kelvin's instructions were somewhat suspect, however, as it was later revealed he was using the alleged sickness as a means of keeping Desmond confined within The Swan. ("Live Together, Die Alone, Part 1") The vaccine kit found by Charlie in the supply drop, however, also contained instructions that a shot should be given every nine days, supporting at least part of Kelvin's story. ("Three Minutes")

A DHARMA worker uses an injection gun on a new arrival.

Claire theorized later that the vaccine was intended to ward off the effects of the Sickness - an unrelated condition that she heard of through Danielle Rousseau. ("Maternity Leave") Claire later ended up suffering from this sickness herself. ("What Kate Does") At a later point, Desmond told Claire that taking the vaccine was worthless and it had no effect. ("Live Together, Die Alone, Part 1")

Desmond, Charlie, Aaron, and possibly Claire were all exposed to the vaccine at various points. It is also highly likely that Ben, Roger Linus, Ethan, and the time shifting survivors who lived with the DHARMA Initiative in the 1970's (including Sawyer, Juliet, Miles, Daniel, Jin, Jack, Kate, and Hurley) were inoculated. In all cases to date the injections have not been known to have produce any adverse effects.

DHARMA Initiative


Throughout the 1970's the DHARMA Initiative was clearly taking some sort of precautions in inoculating new recruits upon their arrival on the Island. These vaccinations appeared to be being carried out by medical personnel from the Staff. ("The Man Behind the Curtain")  ("Namaste") Although not shown, it seems likely that young Ben and his father, Roger Linus were inoculated on their arrival in 1972. Similarly, Jack, Kate, and Hurley were likely inoculated on arrival. It is not known if DHARMA personnel were required to undergo regular ongoing vaccinations for protection.

The Swan

Years later, the Swan station seemed to contain an ample supply of the vaccine. After his arrival on the Island, Desmond was instructed by Kelvin to give himself a shot every nine days and not to venture outside without protection. On being asked why he was donning a HAZMAT suit to go outside on one occasion, Kelvin responded, "So I don't get sick." Desmond faithfully gave himself injections for three years until learning that Kelvin had been staging an elaborate deception in a bid to escape the Island and that no such precautions were actually necessary to go outside. Despite this realization, however, Desmond continued to inject himself with the vaccine for another several weeks until the survivors of Flight 815 blew open the hatch entrance to the station. ("Man of Science, Man of Faith")  ("Live Together, Die Alone, Part 2") It seems likely that Kelvin was also injecting himself regularly with the vaccine during his time at the Swan as to do otherwise would arouse Desmond's suspicion.

Charlie presents the case with the vaccine to Claire.

The Resupply Drop

A case containing a set of vaccine vials and a jet injector was found by Charlie in the supply drop. Charlie tested the vaccine on himself first, then gave to kit to Claire to put her fears to rest about Aaron becoming sick. According to Charlie, instructions in the kit recommended an injection every nine days. ("Three Minutes")

Although not shown, it is likely Claire may have continued to give Aaron injections until his departure from the Island as one of the Oceanic Six.

The Others

Several actions taken by the Others appeared to involve the same vaccine. Some of Ethan's comments indicated the Others had a limited supply which may have been a factor in their recruitment efforts.

Ethan preparing to inject Claire with the unknown vaccine

Claire's abduction

During Claire's abduction, Ethan Rom prenatally injected Claire's baby, Aaron, on several occasions. When Claire asked him about it, Ethan described the substance as a vaccine that the baby needed to prevent him from becoming sick. Although there were numerous vials of the vaccine stored at the Staff, Ethan claimed that there wasn't enough for both Claire and the baby to stay with the Others for the long-term. He explained there was only enough for Aaron. On returning to the station much later with Kate and Danielle, Claire found the station abandoned and that the supply of vaccine had been removed. ("Maternity Leave")

Juliet's serum

Juliet's medical stash found in the jungle.

Main article: pregnancy

After Juliet's arrival at the beach camp, Claire became extremely sick and collapsed, bleeding from the nose. Juliet revealed that on the Island for some reason "the mother's body turns on the pregnancy, treats it as a foreign invader," setting in motion a chain of events leading to the death of both the mother and child. Juliet further described that during Claire's abduction, Ethan injected her with a serum designed to keep pregnant women alive during the late stages of their pregnancy. Juliet claimed that Claire was going into withdrawal and that more of the serum was required or she would die. Juliet also claimed to have designed the serum as part of her work with the Others on the Island.

After convincing the survivors to let her help, Juliet retrieved a hidden stash of medical supplies - containing several vials of what appeared to be the vaccine - and gave Claire an injection. Claire later recovered, although it was later revealed that the entire incident was actually a ploy designed to allow Juliet to gain the survivor's trust. In reality, Claire's "illness" was brought on deliberately by the Others - activating an unknown implant placed in Claire during her abduction. It is unclear if the injection administered by Juliet had any effect in Claire's recovery. ("One of Us")

It is unknown just how much of Juliet's story about Claire's abduction was true. While clearly some events, such as the placement of the implant, took place off-camera during Claire's time at the Staff, the only injections seen to be administered by Ethan were those of the vaccine. As Desmond, Kelvin, and, presumably, a number of other male staff members of the DHARMA Initiative were inoculated and/or were actively taking the same vaccine, it seems unlikely that the vaccine itself had anything to do with pregnancy issues. This would suggest the serum, if it existed, was altogether different.

The Lost Experience

Main article: Sri Lanka Video

In the Sri Lanka Video, part of which was a videotape of a private meeting taken by Rachel Blake, Thomas Mittelwerk explained to volunteers that two villages in Sri Lanka had been intentionally infected with a Hanso-engineered virus, and that the Hanso Foundation's cover story was to provide a treatment vaccine. He explained that the villagers thought they were infected by a virus carried by local macaques and they believed the Hanso workers were bringing them the cure. In fact, Mittelwerk revealed that their goals were a mortality rate of exactly 30%, as well as testing of the deceased to confirm the genetic targets of their virus. Mittelwerk implied that this was tied to saving the world and that these experiments were being done to "perfect this virus."


Juliet prepares to inject fertility drugs into Rachel.

  • A vaccine is a part of a microbe (such as a protein) or a killed or weakened version of the microbe which is used to establish immunity to a disease. A vaccine can be both preventative (administered before a disease is contracted to prevent illness) and therapeutic (administered after a disease is contracted to combat the illness). The immune system recognizes the vaccine as foreign agents, builds up defenses to destroy them, and is thus prepared for when the disease invades again.
  • There are no known post-exposure medications that are given on a weekly basis for years at a time in the real world, although some vaccines (such as the one for Hepatitis B) requires 2 to 3 shots for full effectiveness.
  • Medications in a drug testing phase are often labeled Rx-(testing #). Rx is short for the Latin term recipe, used for medical prescriptions.

An Other infiltrates the camp carrying an injection gun.

  • Part of the vial's label reads: "For Injection, USP". The USP (United States Pharmacopeia) is an independent, science-based, standards-setting public health organization responsible for all prescription and over-the-counter medicines, dietary supplements, and other healthcare products manufactured and sold in the United States.
  • Eko's church distributed vaccines (for polio). His refusal to give a share of the shipment to Nigerian druglords led to his leaving the church. ("The Cost of Living")
  • Juliet injected Rachel with a substance that was similar in color (but with a different label) for fertility purposes. ("Not in Portland")
  • One of the Others who infiltrated the beach camp to kidnap the pregnant women was carrying a jet injection gun with an unknown substance as she looked inside the tent where she believed the women were sleeping. It is likely this contained some sort of sedative to assist the Others in their abduction. ("Through the Looking Glass, Part 1")

Unanswered questions

Unanswered questions
  1. Do not answer the questions here.
  2. Keep the questions open-ended and neutral: do not suggest an answer.
For fan theories about these unanswered questions, see: Vaccine/Theories
  • What is the vaccine intended to combat?
  • Why was Ethan administering injections to Aaron in-utero?

See also