Background
Since 2004, the Global Fund-supported National Malaria Control Programme of Papua New Guinea (PNG) has been implementing country-wide free long-lasting insecticidal net (LLIN) distribution campaigns. In 2009, after the first distribution, only 32.5% of the population used a LLIN, mainly due to an insufficient number of nets available. This study investigated changes in mosquito net ownership and use following the continued free distribution of LLINs across PNG.

Methods
Five villages from each province and 30 households from each village were randomly sampled in a country-wide household survey in 2010/11. A structured questionnaire administered to household heads recorded information on mosquito net ownership and use alongside household characteristics. Revised ownership and access indicators were applied in the analysis to reveal coverage gaps.

Results
The survey covered 1,996 households in 77 villages. Ownership of at least one LLIN was reported by 81.8% of households, compared to 64.6% in 2009 (P = 0.002). Sufficient LLINs to cover all household members (one net per two people) were found in 41.3% of the households (21.4% in 2009, P < 0.001). Of all household members, 61.4% had access to a LLIN within their household (44.3% in 2009 P = 0.002), and 48.3% slept under a LLIN (32.5% in 2009, P = 0.001). LLIN use in children under five years amounted to 58.2%, compared to 39.5% in 2009 (P < 0.001). Significant regional differences in coverage and changes over time were observed. A recent LLIN distribution was a key determinant of LLIN ownership (adj. OR = 3.46) while families in high quality houses would frequently not own a LLIN (adj. OR = 0.09). Residents were more likely to use LLINs than household guests (OR = 2.04).

Conclusions
Repeated LLIN distribution has led to significant increases in mosquito net ownership and use with few regional exceptions. Additional nets are required in areas where access is low, while major efforts are required to encourage the use of existing nets in region where access is high but use remains low. Complementary vector control approaches should also be considered in such settings.