As vaccination coverage increases (1985 through about 1991) we see a decrease in the power of cycles of approximately 4 years.
We begin to see an increase in this power after the introduction of a P vaccination in 2004, suggesting transmission patterns similar to those observed in the pre-transmission-blocking vaccine era A second line of evidence comes from changes in age-specific attack rates in the US and UK.
(2014) [ transmission to explore the public health consequences of asymptomatic transmission.
We see an increase in the birth rate after the switch to a P, as expected given the rise in incidence; however, we see a decrease in the sampling rate after the switch to a P.
) presents a challenge to both public health practitioners and scientists trying to understand the mechanisms behind its resurgence.
Three main hypotheses have been proposed to explain the resurgence: 1) waning of protective immunity from vaccination or natural infection over time, 2) evolution of We find that: 1) the timing of changes in age-specific attack rates observed in the US and UK are consistent with asymptomatic transmission; 2) the phylodynamic analysis of the US sequences indicates more genetic diversity in the overall bacterial population than would be suggested by the observed number of infections, a pattern expected with asymptomatic transmission; 3) asymptomatic infections can bias assessments of vaccine efficacy based on observations of ], accessed 20 January 2015).
This mismatch between the birth rate and sampling rate indicates that, despite increasing numbers of new cases, the fraction of cases identified decreases.
Importantly, the estimated decrease in the sampling rate coincides with the time-window containing the largest number of sampled bacteria and in an era with the greatest accuracy in the laboratory methods used in diagnosing in the population after the US switched from the w P to the a P vaccine.