The second wave of 2009 pandemic influenza A(H1N1) in New Zealand, January-October 2010.

This paper uses data from multiple surveillance systems to describe the experience in New Zealand with the second complete wave of pandemic influenza A(H1N1)2009 in 2010. Measures such as hospitalisation rates suggest the overall impact of influenza A(H1N1)2009 in 2010 was between half and two thirds that of the first wave in 2009. There was considerable regional and sub-regional variation with a tendency for higher activity in areas that experienced low rates in 2009. Demographic characteristics of the second wave were similar to those in 2009 with highest rates seen in children under the age of five years, and in indigenous Māori and Pacific peoples. Hospital services including intensive care units were not under as much pressure as in 2009. Immunisation appears to have contributed to the reduced impact of the pandemic in 2010, particularly for those aged 60 years and older.