A study shows that a loss of immunity caused flu and RSV peaks to occur earlier in the season before returning to pre-pandemic patterns.
RT’s Three Key Takeaways:
- Immunity Loss and Surge Timing: Researchers found that the lack of seasonal respiratory infections during the pandemic led to a buildup of susceptible individuals, causing subsequent surges to occur earlier in the season.
- Cardiovascular Link: The study suggests that respiratory infections are key drivers for the timing of seasonal surges in cardiovascular deaths, as heart-related mortality patterns closely mirrored the shifts in infection rates.
- Return to Normalcy: Data indicates that the timing of respiratory surges is gradually returning to pre-pandemic patterns within one or two seasons as population-level immunity stabilizes.
German researchers have identified why the timing of seasonal respiratory surges and heart-related deaths shifted following the COVID-19 pandemic, according to a study published in PLOS Global Public Health.
Researchers at the Max Planck Institute for Evolutionary Biology analyzed 14 years of data on infection and death rates in Germany. They found that pre-pandemic respiratory infections, such as influenza and respiratory syncytial virus (RSV), typically peaked in February and March. However, after pandemic interventions like social distancing and masking disrupted transmission, these surges shifted to December or earlier.
The analysis used epidemiological modeling to show that a population-level loss of immunity after a skipped seasonal surge led to a buildup of susceptible hosts. This larger pool of hosts resulted in higher transmission earlier in the season. According to the study, seasonal transmission variations provide a window of opportunity for a surge, and the size of the susceptible population determines exactly when that surge occurs.
The researchers also found that surges in all-cause mortality, particularly from cardiovascular disease, shifted earlier in alignment with respiratory infections. This adds to evidence that respiratory infections are a significant risk factor for cardiovascular problems and may drive the timing of seasonal heart-related deaths.
“We were even more surprised to see that the seasonal dynamics of all-cause mortality, which is dominated by cardiovascular diseases, closely followed the shift in timing of respiratory infections,” said Sieber and Traulsen, researchers at the Max Planck Institute for Evolutionary Biology, in a news release. “This adds to the growing evidence that respiratory infections are an important risk factor for cardiovascular problems.”
The study indicates that these peak weeks are gradually resuming pre-pandemic timing as immunity levels stabilize. Based on these findings, the researchers emphasized the importance of monitoring infection history, improving vaccination coverage, and maintaining healthcare readiness for shifting seasonal patterns.
