Post by Nadica (She/Her) on Jun 24, 2024 8:32:11 GMT
Evidence of immunity gap: Decline in antibodies against M. pneumoniae during the COVID-19 pandemic - Published June 18, 2024
Dear editor,
In this journal, Liang et al. and Li et al. reported M. pneumoniae infections in children of all ages declined during the COVID - 19 pandemic (2020-2022).1, 2 In 2021-2022, M. pneumoniae maintained a low incidence, contrasting with the resurgence observed in other respiratory pathogens.3, 4 Since April 2023, a rise in M. pneumoniae infection numbers was observed across numerous European and Asian countries.5 In October and November 2023, hospitals in China witnessed a surge in cases of M. pneumoniae among children, leading to an overwhelming number of pediatric emergency admissions in most healthcare facilities.6 In Suzhou, we witnessed a resurgence of M. pneumoniae in 2023, occurring three years after the onset of COVID-19 pandemic restrictions (Supplementary Fig 1). Notably, the demographic affected during this resurgence comprised older children, distinguishing it from the age distribution observed in the previous endemic period (Supplementary Fig 2). The resurgence of M. pneumoniae over three years after the initiation of COVID-19 pandemic restrictions was notably atypical, considering that many other respiratory pathogens experienced an earlier resurgence.
Previous studies have shown that the resurgence of M. pneumoniae was due to macrolide-resistant epidemic clones in China.7, 8 However, these macrolide-resistant clones were already prevalent in China before the COVID-19 pandemic and were also widespread in our region (Supplementary Fig 3). We believe that the main factor increasing susceptibility to M. pneumoniae infection is the immunity gap, characterized by waning humoral immunity. The pandemic provides a unique opportunity to investigate M. pneumoniae immunity following an extended period (2020-2022) with low exposure to the microbe.
To investigate this effect, we systematically collected serum samples from a cohort of 4710 children (Supplementary Fig 4), aged 1 to 14 years, who participated in pediatric check-ups or non-infectious diseases at two tertiary children’s hospitals in Suzhou during the periods of 2018, 2019, 2021 and 2023. The serum samples were collected in Feb-Apr for each year within the study periods (months before the typical M. pneumoniae seasons, Supplementary Fig 1). Anti-M. pneumoniae IgG Human in ELISA kit (Institute Virion/Serion, Würzburg, Germany) was used for the qualitative measurement of M. pneumoniae IgG. IgG concentrations were log₁₀ transformed for statistical analyses. Kruskal-Wallis test (SPSS version 29; IBM, Armonk, NY, USA) was used to compare antibody concentrations between sampling timepoints. P values are reported for timepoints differences after adjusted to Bonferroni procedures.
There were no significant differences in IgG concentrations between sampling timepoints in 2018 and 2019 in all age groups (all P>0.05, Supplementary Fig 5). From 2019 to 2023, there was a significant decrease in antibody levels across all age groups (all P<0.05, Supplementary Fig 6). Interestingly, the decrease was more pronounced for the interval between timepoints 1 and 2 when compared to the decrease between timepoints 2 and 3 in children aged 1-2 years (P < 0.001 vs P = 0.87), 3-5 years (P < 0.001 vs P = 0.99), and 6-8 years (P < 0.001 vs P = 0.37). Conversely, the difference was greater for the interval between timepoints 2 and 3 for children aged 9-11 years (P = 0.89 vs P = 0.03) and 12-14 years (P = 0.78 vs 0.006).
These data, for the first time, provide evidence of M. pneumoniae immunity gap following an extended period with low exposure to the microbe. The temporary collective immunity within the population (especially older children) could have played a role in suppressing the resurgence of the infection for an extended period. The convergence of new susceptible birth cohorts and waning immunity against M. pneumoniae serves to widen the immunity gap, consequently elevating the risk of M. pneumoniae outbreaks in 2023 (Supplementary Fig 7).
It is essential to continue monitoring immunity levels and understanding the immune response's persistence following M. pneumoniae infection, especially in light of the long-term effects post-COVID-19 pandemic. International collaboration and information sharing are crucial in addressing the epidemiological changes of M. pneumoniae. Cross-regional cooperation will enhance our understanding of the broader scope of M. pneumoniae outbreaks, facilitate the sharing of experiences and best practices, and enable a collective response to this issue. By maintaining vigilance and fostering global partnerships, we can improve our strategies for preventing and treating M. pneumoniae infections, ultimately protecting public health more effectively.
Dear editor,
In this journal, Liang et al. and Li et al. reported M. pneumoniae infections in children of all ages declined during the COVID - 19 pandemic (2020-2022).1, 2 In 2021-2022, M. pneumoniae maintained a low incidence, contrasting with the resurgence observed in other respiratory pathogens.3, 4 Since April 2023, a rise in M. pneumoniae infection numbers was observed across numerous European and Asian countries.5 In October and November 2023, hospitals in China witnessed a surge in cases of M. pneumoniae among children, leading to an overwhelming number of pediatric emergency admissions in most healthcare facilities.6 In Suzhou, we witnessed a resurgence of M. pneumoniae in 2023, occurring three years after the onset of COVID-19 pandemic restrictions (Supplementary Fig 1). Notably, the demographic affected during this resurgence comprised older children, distinguishing it from the age distribution observed in the previous endemic period (Supplementary Fig 2). The resurgence of M. pneumoniae over three years after the initiation of COVID-19 pandemic restrictions was notably atypical, considering that many other respiratory pathogens experienced an earlier resurgence.
Previous studies have shown that the resurgence of M. pneumoniae was due to macrolide-resistant epidemic clones in China.7, 8 However, these macrolide-resistant clones were already prevalent in China before the COVID-19 pandemic and were also widespread in our region (Supplementary Fig 3). We believe that the main factor increasing susceptibility to M. pneumoniae infection is the immunity gap, characterized by waning humoral immunity. The pandemic provides a unique opportunity to investigate M. pneumoniae immunity following an extended period (2020-2022) with low exposure to the microbe.
To investigate this effect, we systematically collected serum samples from a cohort of 4710 children (Supplementary Fig 4), aged 1 to 14 years, who participated in pediatric check-ups or non-infectious diseases at two tertiary children’s hospitals in Suzhou during the periods of 2018, 2019, 2021 and 2023. The serum samples were collected in Feb-Apr for each year within the study periods (months before the typical M. pneumoniae seasons, Supplementary Fig 1). Anti-M. pneumoniae IgG Human in ELISA kit (Institute Virion/Serion, Würzburg, Germany) was used for the qualitative measurement of M. pneumoniae IgG. IgG concentrations were log₁₀ transformed for statistical analyses. Kruskal-Wallis test (SPSS version 29; IBM, Armonk, NY, USA) was used to compare antibody concentrations between sampling timepoints. P values are reported for timepoints differences after adjusted to Bonferroni procedures.
There were no significant differences in IgG concentrations between sampling timepoints in 2018 and 2019 in all age groups (all P>0.05, Supplementary Fig 5). From 2019 to 2023, there was a significant decrease in antibody levels across all age groups (all P<0.05, Supplementary Fig 6). Interestingly, the decrease was more pronounced for the interval between timepoints 1 and 2 when compared to the decrease between timepoints 2 and 3 in children aged 1-2 years (P < 0.001 vs P = 0.87), 3-5 years (P < 0.001 vs P = 0.99), and 6-8 years (P < 0.001 vs P = 0.37). Conversely, the difference was greater for the interval between timepoints 2 and 3 for children aged 9-11 years (P = 0.89 vs P = 0.03) and 12-14 years (P = 0.78 vs 0.006).
These data, for the first time, provide evidence of M. pneumoniae immunity gap following an extended period with low exposure to the microbe. The temporary collective immunity within the population (especially older children) could have played a role in suppressing the resurgence of the infection for an extended period. The convergence of new susceptible birth cohorts and waning immunity against M. pneumoniae serves to widen the immunity gap, consequently elevating the risk of M. pneumoniae outbreaks in 2023 (Supplementary Fig 7).
It is essential to continue monitoring immunity levels and understanding the immune response's persistence following M. pneumoniae infection, especially in light of the long-term effects post-COVID-19 pandemic. International collaboration and information sharing are crucial in addressing the epidemiological changes of M. pneumoniae. Cross-regional cooperation will enhance our understanding of the broader scope of M. pneumoniae outbreaks, facilitate the sharing of experiences and best practices, and enable a collective response to this issue. By maintaining vigilance and fostering global partnerships, we can improve our strategies for preventing and treating M. pneumoniae infections, ultimately protecting public health more effectively.