CDC: US Flu Vaccine Effectiveness (VE) Data 2018-2019; estimates are that effectiveness of the flu shot declines by about 18% for each 28 days’ post-vaccination; 15-64 years, means '0' VE at 6 mth

We see most VE begins less than 50% and this would mean that by 2 months post shot, there is '0' VE and it may enter negative efficacy territory; so if 29% all ages, by 1 month, it is '0'& VE

Work done by researchers from the Kaiser Permanente Vaccine Study Center and the Harvard School of Public Health estimated vaccine effectiveness declined by about 18% for every 28-day period after vaccination. A study done by scientists at the Centers for Disease Control and Prevention and elsewhere showed that the vaccine’s protection against flu that is severe enough to trigger hospitalization decreases by between 8% and 9% per month after vaccination. In older adults, who are more likely to get seriously ill from flu, the decline happened at a rate of about 10% to 11% per month.’

This means VE of:

• 29% for all ages

• 48% for children aged 6 months through 8 years

• 7% for children ages 9 through 17

• 25% for adults between the ages of 18 and 49

• 14% for those 50 to 64

• 12% >=65

US Flu VE Data for 2018-2019

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8499703/pdf/ciab045.pdf