A crucial factor in the pandemic’s future trajectory will be the role of vaccinated people in the transmission, as global vaccination coverage continues to climb.
How much of a role vaccinated individuals play in the spread of SARS-CoV-2, including the B.1.617.2 (Delta) variant, is uncertain.
In a study conducted in a Texas prison, researchers discovered that those who have been vaccinated are still carriers of the coronavirus, albeit to a lesser amount.
COVID-19 vaccines have been shown to prevent serious sickness and death, but it was unknown to what extent vaccinated individuals would carry the infection until recently.
The cumulative incidence of infection in two afflicted housing units in a recent Delta variant outbreak at a federal prison in Texas was 74 percent; it was 93 percent and 70 percent among unvaccinated and vaccinated incarcerated inmates, respectively.
This study compares the transmission potential of fully vaccinated and non-vaccinated people over time using reverse transcription-polymerase chain reaction (RT-PCR) and viral culture characteristics as surrogate markers.
Out of 189 participants who were eligible, 96 people with SARS-CoV-2 infection volunteered to engage in serial specimen collection; one participant had a single positive diagnostic test (Ct=36.2) followed by seven negative diagnostic tests and no symptoms, therefore they were ruled out as a non-case.
In the study, 78 (82 percent) of the 95 subjects were fully vaccinated against SARS-CoV-2, 15 (16 percent) were unvaccinated, and 2 (percent) were partially vaccinated but later classified as not fully vaccinated.
The Pfizer vaccine was given to the majority of the fully immunized patients (73 percent) whereas the Moderna vaccine (18 percent) and the Janssen to lesser proportions (9 percent).
Since the last RT-PCR positive result, there have been no notable changes. In completely vaccinated subjects, the median duration of RT-PCR positive was 13 days, compared to 13 days in non-vaccinated participants.
Furthermore, in participants with a known history of prior SARS-CoV-2 infection (regardless of vaccination), the time since the last RT-PCR positive result was 10 days, compared to 13 days in participants with no known prior infection.
The median duration of positivity among fully vaccinated participants was ten days for Moderna vaccine recipients, thirteen days for Pfizer recipients, and thirteen days for Janssen vaccine recipients; and thirteen days for participants fully vaccinated more than 120 days prior to the outbreak, compared to eleven days for those vaccinated 120 days or less prior to the outbreak.
The number of days from onset increased the Ct values from RT-PCR-positive specimens. Ct values in completely vaccinated individuals’ specimens increased from a median of 26.4 on day 1 to a median of 32.9 on day 10. Ct values in non-fully vaccinated participants’ specimens, on the other hand, climbed from a median of 28.5 on the day of onset to a median of 34.5 on day ten.
There was no statistically significant change in Ct values by vaccination status across the course of infection after Bonferroni correction. Furthermore, when Ct levels were stratified by vaccine product, time since immunization, or known past SARS-CoV-2 infection, no significant variations in Ct values were detected.
Between fully vaccinated subjects (median: five days) and those who were not fully vaccinated, there was no statistically significant difference in the duration of viral culture positive.
Fully vaccinated participants who received the Moderna vaccine had a lower culture positivity rate than those who received Pfizer or Janssen vaccines, according to cumulative hazard functions. Despite this, there was no discernible difference in vaccine recipients between Pfizer and Janssen.
When the duration of culture-positive was stratified by time since vaccination or known prior infection, no statistically significant differences were detected in the length of culture-positive.
Those who had previously been unwell with COVID-19 were the only exceptions; their virus remained active for no more than 10 days, regardless of immunization.
The researchers stressed that there is no statistically significant difference in coronavirus transmission between fully vaccinated and unvaccinated people.
As a result, regardless of the people’s vaccination status, COVID-19 protective measures should be implemented, particularly in closed environments (prisons, hospitals, and nursing homes).
Source: https://doi.org/10.1101/2021.11.12.21265796
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