partially active – the HIV treatment in question will work against this virus but this is reduced compared to wild-type HIV. This is the same as partial resistance, or intermediate resistance etc.
Glossary
Selected words and phrases
undetectable – an amount smaller than a test can measure. For viral load tests, this means below 400 or, more commonly, below 50 copies/mL, depending on the make of test. In research laboratories, some very sensitive tests can measure down to 1 copy/mL.
grade/grading – the grade of hepatitis infection refers to the amount of inflammation in liver tissue, found by a biopsy. It is usually measured on the Ishak scale from 1-18) where 0 is none and 18 is the maximum. See staging.
amino acids – amino acids are the building blocks of proteins. DNA codes for amino acids. Three nucleotides (segments of the genetic code) make one amino acid. Amino acids are critical to life, and have many functions in the way your body works.
On-demand dosing – a term for taking medicines only at times linked to a relevant event.
On-demand dosing for PrEP is also called “event-based dosing” (EBD).
For example, on-demand dosing for PrEP (to prevent HIV transmission) involves taking PrEP before sex and then for several days after sex.
For many years, on-demand dosing referred to 2:1:1 dosing. This was an option for cisgender gay and bisexual men using PrEP. This involves starting with a double dose (two pills), taken 24 to 2 hours before sex, and then single daily doses for the two days after sex.
In 2025, UK (BASHH) and European (EACS) PrEP guidelines included 2:7 on-demand dosing for cis and trans women and other transgender and non-binary people.