Vaccine Alone Insufficient Against Breakthrough Infections... US New Cases Surge Due to 'Delta Variant'

On the 26th (local time), a notice stating that entry is not allowed without wearing a mask is posted at a store in New York, USA.
[Photo by Yonhap News]

[Asia Economy Reporter Seoyoung Kwon] The U.S. Centers for Disease Control and Prevention (CDC) has once again emphasized that vaccination alone cannot completely prevent the transmission of COVID-19.

On the 30th (local time), CDC researchers announced that they analyzed 469 COVID-19 cases linked to various events held in Bristol County, Massachusetts, from July 3 to 17, which included the Independence Day holiday. Those infected with COVID-19 at that time were reported to have attended various crowded indoor and outdoor events.

Among the infected individuals analyzed, 74% (346 people) had already been vaccinated. Of these, 159 had received the Pfizer vaccine, 131 the Moderna vaccine, and 56 the Janssen vaccine. At that time, four-fifths (279 people) of those who experienced breakthrough infections reported having symptoms.

Additionally, when comparing samples from 127 people who had completed vaccination and experienced breakthrough infections with 84 people who were unvaccinated or had only received one dose before infection, the amount of virus in the nasal passages was found to be similar. The Washington Post (WP) described this as "key evidence supporting the possibility that vaccinated individuals spread highly transmissible variants, causing resurgence."

However, among all analyzed infected individuals, only five were hospitalized, and there were no deaths. This aligns with other studies suggesting that while vaccines may not completely prevent infection, they can help prevent hospitalization or severe symptoms after infection.

The researchers further recommended, "Health authorities and event organizers should continuously review additional measures such as limiting the number of participants based on COVID-19 transmission rates and vaccination coverage." They also advised, "Health authorities in areas with low transmission rates should consider expanding preventive measures, such as mandating mask-wearing regardless of vaccination status."

Earlier, on the 27th, the CDC revised its guidelines to recommend that even vaccinated individuals wear masks in indoor public places in areas with high COVID-19 transmission rates. This reversal came just over two months after the mid-May announcement that fully vaccinated people did not need to wear masks indoors or outdoors.

The renewed emphasis on mask-wearing is attributed to the spread of the Delta variant. During this study, genomic analysis of samples from 133 infected individuals estimated that 89% (119 people) were infected with the Delta variant. Additionally, the pace of vaccination in the U.S. has stalled. As of the 28th, the average daily number of vaccinations over the past week was about 535,000, a significant decrease compared to early April when daily vaccinations reached as high as approximately 4,435,000.