DENVER (KDVR) — Rates of COVID reinfection are still early, but according to a June study from the Irish Journal of Medical Science, the omicron sub-variants are likely among the most transmissible yet.

Sub-variants of the COVID omicron variant, BA.4 and BA.5, are now a majority of national cases. According to data from the Colorado Department of Public Health and Environment, the state’s positivity rate, or the number of COVID tests that are coming back positive, was 12.97% as of July 5. The metric has been on the rise since June 24, when it sat at 11%.

As the pandemic went on, COVID strains have become more likely to bypass immunity derived from previous infection or from vaccination. Vaccines wear off, and the virus itself only has immune people to select from anyway. The number of people who were previously infected naturally rises.

Among the original COVID strain cases examined in the study, only 0.46% were reinfection cases.

The next dominant strain was three times as likely to infect a previously infected person. Among the delta cases, 1.16% were reinfections.

The less severe omicron variant was also the most likely to result in reinfection. Thirteen percent of omicron cases were among previously-infected people.

Most early data says the new BA.4 and BA.5 omicron sub-variants are especially skilled at slipping past immunity from previous infections or vaccines.

The new strains’ ability to sneak past immunity could be one of the factors adding to a growing hospital load of vaccinated people.

According to estimates from the Colorado Department of Public Health and Environment, over half the state’s COVID-positive hospital patients have been vaccinated.