A new Covid variant, HV.1, has replaced EG.5 as the dominant strain in the United States, according to data released by the Centers for Disease Control and Prevention (CDC). This comes as the rollout of the updated Covid shots, which offer some protection against HV.1, has seen a slow uptake among the population.

HV.1 and EG.5 are genetically similar versions of the omicron variant, both descended from XBB. The updated Covid vaccines from Pfizer and Moderna, targeting the XBB.1.5 descendant, are believed to provide cross-protection against the currently dominant HV.1 strain. Dr. Scott Roberts, an infectious disease specialist at Yale Medicine, emphasized the vaccines may not be a perfect match but are still a good match as they belong to the same family of variants.

However, only around 3.5% of the U.S. population, approximately 12 million people, have received the new Covid shots since they became available in mid-September. This low uptake is a cause for concern among experts. Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston, worries about the low frequency of high-risk individuals, including older adults and immunosuppressed individuals, receiving the updated shots.

Several factors have contributed to the slow vaccine rollout. Besides accessibility and hesitancy issues observed in previous campaigns, this is the first time these vaccines are part of the commercial market rather than being federally ordered, distributed, and funded. The logistical complications have added obstacles, but Dr. Barouch believes the low uptake reflects dwindling public concern about Covid.

The dominance of HV.1 is likely due to its slightly better transmissibility or ability to infect those with prior immunity to Covid, making it more prevalent. However, scientists do not consider it alarming enough to change booster recommendations so far.

Since the emergence of omicron in December 2021, all dominant variants have descended from it, and this ongoing evolution is expected to continue. While the CDC recommends the updated shots for everyone aged 6 months and older, experts stress the importance of getting high-risk individuals vaccinated, as they are more likely to strain the healthcare system.

In the previous vaccine rollout last fall, more than 19 million people (5.5% of the population) had received the bivalent booster within six weeks of its release in September 2022. However, the old booster is no longer available as it targeted earlier versions of omicron.

The current rollout faces challenges related to insurance coverage, shipment delays, and appointment cancellations. Some insurers were not updated in time for billing systems, leading to confusion and payment disputes. Delayed vaccine shipments and limited availability for young children have also caused appointment cancellations. Experts fear that people who encounter roadblocks may give up on trying to get vaccinated.

Although Covid transmission rates appear to be slowing, the virus is still causing severe illness among those infected. Hospitals continue to admit patients in critical condition, with some on mechanical ventilators. Experts stress the need to prioritize vaccination for high-risk individuals to alleviate the strain on the healthcare system.

Efforts to increase vaccination rates and address the challenges in the rollout continue, but there is concern that the low uptake of the new Covid shots may hinder the overall control of the pandemic.