New SARS-CoV-2 variant predominates in the United States

Bill Shaw

The SARS-CoV-2 virus that causes COVID-19 continues to evolve, with a new variant becoming predominant in the United States. Data from the Centers for Disease Control and Prevention showed that the new viral variant, called KP.2, made up 28.5 percent of COVID-19 cases by May 11. It maintained that level as of May 25. 

The viral variant with the next highest percentage of cases is also new. It is called KP.3, and as of May 25, it makes up an estimated 12.7 percent of cases.

The previously predominant variant was JN.1. It now makes up only 8.4 percent of cases in the US. Wastewater surveillance data also demonstrates a rapid increase in the prevalence of KP.2, although in wastewater as of May 11, JN.1 still predominates.

To date, only one study has examined the properties of the KP.2 variant. Published in The Lancet Infectious Diseases under the category of “Correspondence”, it is a brief study that provides early results about the variant obtained as quickly and rigorously as possible to inform policy and the public.

First, the researchers used surveillance data to estimate the reproduction number or Re of the virus. The reproduction number is the number of new infections that are expected to occur from each existing infected individual in the population. A value greater than 1 means that the virus will spread exponentially.

The researchers estimated Re values for the United States, United Kingdom, and Canada of that are 1.22, 1.32, and 1.26 times higher than the Re values for the previously predominant JN.1 virus, respectively. They reported only the relative Re with respect to JN.1, not the absolute Re number.

This result means that the new KP.2 variant is more infectious than its predecessor, making it more likely to spread among the population. Notably, in the United Kingdom, JN.1 had a Re that was 1.261 times higher than its predecessor prior to becoming the predominant strain. Thus the virus continues to become more contagious.

Artist’s conception of the spike proteins that allow SARS-CoV-2 to invade human cells. [Photo by Emanresucamit / CC BY-SA 4.0]

Notably, the study was done prior to KP.2 becoming the predominant viral variant in the U.S. On the basis of their findings, the researchers correctly concluded that KP.2 had high potential to become the predominant strain worldwide. Indeed, their prediction has come true already in the United States.

The researchers also conducted neutralization assays to study the degree to which existing immunity to SARS-CoV-2 variants, whether through infection or vaccination, was protective against KP.2. These assays use blood serum obtained from vaccinated and previously infected individuals. In this study, the sera collected contained antibodies against the previous strains of virus including XBB 1.5, EG.5.1, HK.3, and JN.1.

The researchers then combined the serum with cultures of cells that are infected with the same strains of the virus. They then quantified how much serum was required to neutralize the virus, using the 50 percent neutralization titer or NT50. Lower values of NT50 mean that greater quantities of serum are required to neutralize 50 percent of the virus.

The researchers found significantly lower NT50 values for the KP.2 variant. The significance of this result is that pre-existing immunity to previous variants is less protective against KP.2. Therefore, KP.2 has an increased immune escape ability as well as greater infectiousness.

The net effect is that the recent predominance of KP.2 is in line with its known properties per the lone study to examine it thus far.

Although the “herd immunity” approach to the pandemic has already been overwhelmingly discredited, it is demolished even further by the emergence of KP.2, yet another highly infectious SARS-CoV-2 variant that is escaping pre-existing immunity to previous variants.

So long as the criminal “let it rip” policy of the ruling class is in place, SARS-CoV-2 will continue to evolve new variants with varying levels of infectiousness, severity of infection, and probability of causing Long COVID. Scientifically, there is no reason to expect that future variants will be less dangerous: each new variant poses a risk that the virus will be more deadly and cause more long-term disability.

Therefore, each new variant immediately poses the same set of urgent questions as the last variant. How infectious is it? How severe is the infection? How much protection does pre-existing immunity provide? What is the probability of developing Long COVID after infection?

The indifference of the ruling class to the suffering and death caused by the virus is demonstrated by the dismantling of the public health system to let a novel virus continue to evolve into potentially more dangerous forms. The CDC’s COVID Data Tracker web site illustrates this disregard for human life, saying, “New variants of SARS-CoV-2 are expected to continue to emerge.” In other words, the ruling class is willing to risk newer and potentially more deadly variants to evolve, no matter the consequences.