Other factors contributing to the rapid increase in new coronavirus infections
In addition to vaccine fatigue, the recent surge in the number of coronavirus disease (COVID-19) infections may be due to several other factors.
First, there is a decline in herd immunity. Immunity from vaccines usually declines over a period of up to a year after each shot. Combined with recent delays in uptake of booster vaccines, it may be difficult to maintain herd immunity.
The Singapore government has updated its COVID-19 vaccine recommendations, encouraging people over six months of age to receive a booster shot in 2023 or 2024.
The currently updated booster vaccine can provide effective immunity against Omicron XBB 1.5. It also provides cross-protective immunity not only to submutants but also to other circulating Omicron submutants, reducing the risk of severe disease.
As the World Health Organization (WHO) has reported, the recent surge in the JN.1 subvariant is likely to displace other subvariants and spread more primarily around the world.
Although evidence of cross-protective immunity of the latest vaccines against the JN.1 subvariant is still lacking, both the WHO and the US Centers for Disease Control and Prevention expect the latest COVID-19 vaccines to remain effective. are doing. This is based on limited differences in the genetic variation of the virus assessed through next-generation sequencing technology as part of a continuous surveillance strategy.
With new subvariants constantly evolving, populations with reduced herd immunity may experience a new surge of cases each year, similar to winter influenza infections in the northern and southern hemispheres.
Second, year-end travel and celebratory gatherings increase the risk of exposure to and transmission of COVID-19 in a specific location over a short period of time, akin to a superspreading event.
Finally, since early 2023, we have been in an epidemic period, which has led to increased complacency. A “false sense of security” reduces motivation to receive additional booster shots. This also led to a decline in compliance with personal precautions over time, such as wearing masks in crowded indoor environments, self-isolating when sick, and practicing frequent hand washing with soap. .