Quickie summary of flu in Texas for those who asked.
The 2008–2009 flu season was relatively mild, with a small peak in late January/early February (blue line). But in April of 2009, the first cases of H1N1, later to be a pandemic, were identified in Guadalupe County. Cases dropped over the summer, then spiked up again in late August/early September (orange line). The remainder of the season stayed mild. The 2010–2011 season saw cases start to peak in mid-January into February
April is usually the end of flu season. But in April of 2009, 2 individuals in Guadalupe County were identified with a novel strain of flu: H1N1. An initial outbreak requiring some schools to close tapered off as summer arrived. Cases peaked again by early October. The first doses of vaccine became available in October and cases began to decline. Note this graph shows April — March. Flu season graphs show Oct-Sept.
The efficacy of the 2011–2012 vaccine was about 50%, leading to a relatively mild flu season (blue line). The increase in cases again began in late January into February but stayed low. In 2011, cases started to increase in mid-December. While not usually the peak, it’s not uncommon to see a post-Thanksgiving spike for flu, followed by. A much bigger spike in January.
In 2013, cases peaked early, in December, but declined throughout January. The primary strain circulating was H1N1, and the 2013–2014 season saw the most severe disease in adults aged 18–64, similar to the 2009 pandemic. The efficacy of that season’s vaccine was 62%. The severity of that season was likely due to a lack of vaccination.
2014 saw a spike in late November, followed by another spike in January. Overall the effectives of the vaccine for the 2014–2015 season was less than 30%.
2015–2016 and 2016–2017 followed the more common patterns of peaks in late January, with more severity in 2017. The vaccine that year was about 40% effective.
2017–2018 was a moderate to high severity season. There was a peak in the end of December followed by a bigger peak in late Jan/Feb.
The 2018–2019 season was less severe, but also lower vaccine efficacy due to antigenic drift. https://medium.com/@cheriserohrallegrini/lets-talk-flu-vaccine-efficacy-b46baf5e3298
The 2019–2020 season followed a similar pattern.