Immunity Gain Speed

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Immunity Gain Speed is a stat: The speed at which this character gains immunity to diseases. If this is too slow, the character will die from the disease before developing immunity. Its default value is 100%. The value shown in-game is rounded to the nearest whole percent, while exact value is used in calculations.

While this stat can be seen in-game, the actual immunity gain speed, measured in percentage per day, is hidden but can be deduced from thorough observations. It is calculated as a product of:

  • Base immunity gain speed for the particular disease. For example, 23.88% per day for human Flu.
  • InfectionLuck, a pseudorandom factor ranging from 80% (Bad luck) to 120% (Good luck). It is set independently for each disease instance (when multiple pawns are affected by a disease outbreak, each of them gets their own disease instance). Wound infections in different organs of the same pawn are different instances, but only InfectionLuck of the oldest active infection comes into play (and only one infection immunity develops in organism, opposing all infection instances).
Technical details. InfectionLuck is not stored in save file. Instead, it is calculated as a pseudorandom value depending on the world's seed (seedString) and disease's hediff ID (loadID). For example, it is ≈81.7511% for seed "InfectionLuck" and ID of 1947.
  • Immunity Gain Speed stat.

Immunity gain speed is not affected by medical tend quality.

Stat factors[edit]

Immunity Gain Speed stat is determined by many factors multiplicatively.


Blood Filtration: 50% importance. No allowed defect. No Max. So,

Blood filtration factor = Blood Filtration ÷ 2 + 50%

Notable facts:

  • Malaria progressively reduces Blood Filtration.
  • A missing Kidney reduces Blood Filtration by 50%. This alone results in a Blood filtration factor of 75%.
  • Cancer progressively reduces efficiency in the body part affected, potentially reducing Blood Filtration if it is in the Kidneys or Liver.
  • Luciferium adds 70% to Blood Filtration. This alone results in a Blood filtration factor of 135%.
  • Detoxifier kidneys each add 5% Blood Filtration each compared to a healthy kidney. This alone results in a blood filtration factor of 102.5% (105% with two).



  • 100%: Fed or Hungry
  • 90%: Urgently Hungry (corresponds to Ravenously Hungry)
  • 70%: Starving (corresponds to Malnourished)


Rest need:

  • 100%: Rested
  • 96%: Tired (corresponds to Drowsy thought)
  • 92%: Very tired (corresponds to Tired thought)
  • 80%: Exhausted (corresponds to Exhausted thought)

In Bed:

Note that quality of the bed only influences the rest effectiveness, not the immunity gain speed.


  • 100%: Not resting. Also, when downed, despite visually lying.
  • 110%: Resting, sleeping or skygazing (cloudwatching, stargazing, etc).


Generally, the multiplier for age follows a curve defined by 5 points.

Age Multiplier
0.65 * Life Expectancy 100%
0.80 * Life Expectancy 95%
1.00 * Life Expectancy 90%
1.20 * Life Expectancy 80%
1.50 * Life Expectancy 50%

As life expectancy is 80 for Humans, the following are approximate values for them.

Age Immunity Gain Speed
<54 100%
54 99%
56 98%
59 97%
61 96%
63 95%
66 94%
69 93%
72 92%
76 91%
79 90%
81 89%
83 88%
85 87%
86 86%
88 85%
89 84%
91 83%
93 82%
94 81%
96 80%
97 79%
98 78%
99 76%
100 75%

Past age 100, it continues to gradually decrease until it hits 50% at age 120 and stays at 50% thereafter.


Version history[edit]