Decreases in Both the Seroprevalence of Serum Antibodies and Seroprotection against Japanese Encephalitis Virus among Vaccinated Children

The incidence of Japanese encephalitis(JE)has significantly decreased in China due to JE vaccines.In this study,we investigated the post-JE vaccination seroprevalence and protection provided by vaccinated sera against Japanese encephalitis virus(JEV)to elucidate the persistence and waning of antibodies to JEV among JE-SA14-14-2-vaccinated children.A total of 300 serum samples were collected from vaccinated children aged 3-10 years in Zhaotong,Yunnan,China.The seroprevalence of anti-JEV antibodies was determined by enzyme-linked immune sorbent assay and plaque reduction neutralization test.The highest seropositivity of 82%was observed in vaccinated children during the first 0.5-1.5 years after booster vaccination.Then,the seropositivity began to decline and remained lower than the original level observed in the 0.5-1.5-year group.An association was found between the waning of seroprevalence and elapsed time of the post-booster vaccination.Similarly,the neutralizing antibody(nAb)titres gradually decreased over time,and the levels showed a positive correlation with the protective efficacy in mice.This finding suggests that nAbs play an important role in the antiviral process and that the nAb titre is an adequately credible parameter for evaluating the protective efficacy induced by the JE vaccine.Our results provide data that clarify the persistence and waning of antibodies to JEV,which may help elucidate the pathogenesis of JE.

Incorporating the mutational landscape of SARS-COV-2 variants and case-dependent vaccination rates into epidemic models

Coronavirus Disease(COVID-19),which began as a small outbreak in Wuhan,China,in December 2019,became a global pandemic within months due to its high transmissibility.In the absence of pharmaceutical treatment,various non-pharmaceutical interventions(NPIs)to contain the spread of COVID-19 brought the entire world to a halt.After almost a year of seemingly returning to normalcy with the world's quickest vaccine development,the emergence of more infectious and vaccine resistant coronavirus variants is bringing the situation back to where it was a year ago.In the light of this new situation,we conducted a study to portray the possible scenarios based on the three key factors:impact of interventions(pharmaceutical and NPIs),vaccination rate,and vaccine efficacy.In our study,we assessed two of the most crucial factors,transmissibility and vaccination rate,in order to reduce the spreading of COVID-19 in a simple but effective manner.In order to incorporate the time-varying mutational landscape of COVID-19 variants,we estimated a weighted transmissibility composed of the proportion of existing strains that naturally vary over time.Additionally,we consider time varying vaccination rates based on the number of daily new cases.Our method for calculating the vaccination rate from past active cases is an effective approach in forecasting probable future scenarios as it actively tracks people's attitudes toward immunization as active case changes.Our simulations show that if a large number of individuals cannot be vaccinated by ensuring high efficacy in a short period of time,adopting NPIs is the best approach to manage disease transmission with the emergence of new vaccine breakthrough and more infectious variants.

Infection-acquired versus vaccine-acquired immunity in an SIRWS model

In some disease systems,the process of waning immunity can be subtle,involving a complex relationship between the duration of immunitydacquired either through natural infection or vaccinationdand subsequent boosting of immunity through asymptomatic reexposure.We present and analyse a model of infectious disease transmission where primary and secondary infections are distinguished to examine the interplay between infection and immunity.Additionally we allow the duration of infection-acquired immunity to differ from that of vaccine-acquired immunity to explore the impact on long-term disease patterns and prevalence of infection in the presence of immune boosting.Our model demonstrates that vaccination may induce cyclic behaviour,and the ability of vaccinations to reduce primary infections may not lead to decreased transmission.Where the boosting of vaccine-acquired immunity delays a primary infection,the driver of transmission largely remains primary infections.In contrast,if the immune boosting bypasses a primary infection,secondary infections become the main driver of transmission under a sufficiently long duration of immunity.Our results show that the epidemiological patterns of an infectious disease may change considerably when the duration of vaccine-acquired immunity differs from that of infection-acquired immunity.Our study highlights that for any particular disease and associated vaccine,a detailed understanding of the waning and boosting of immunity and how the duration of protection is influenced by infection prevalence are important as we seek to optimise vaccination strategies.