Single COVID dose may leave virus-naïve vaccinees vulnerable to variants
The first dose of a two-dose COVID-19 vaccine regimen confers a robust immune response against the B117 and B1351 variants in people previously infected with the coronavirus—but not in those in those never infected, according to a new study led by researchers from Imperial College London, Queen Mary University of London, and University College London.
The study, published late last week in Science, involved analyzing blood samples from UK healthcare workers at two hospitals after receiving their first dose of the Pfizer/BioNTech vaccine in December 2020.
Among 23 participants who previously had mild or asymptomatic COVID-19 roughly 40 weeks before, 22 (96%) had T cell responses against the coronavirus spike protein, compared with 16 of 23 (70%) of virus-naïve participants, who also had lower T cell concentrations.
Previously infected participants also had strong B cell and neutralizing antibody responses that could help protect against B117, which was first discovered in the United Kingdom, and B1351, first identified in South Africa. But COVID-19–naïve participants had lower neutralizing antibody responses, which could leave them vulnerable to the variants, the authors said.
In the United Kingdom, most people have received only one dose as part of a strategy to vaccinate more people before offering second doses 12 weeks later.
The researchers said that the findings underscore the importance of a second dose of the vaccine for COVID-19–naïve vaccinees, while one dose may be sufficient for those previously infected, co-senior author Rosemary Boynton, MBBS, PhD, said in an Imperial College London press release.
“Our data show that natural infection alone may not provide sufficient immunity against the variants,” Boynton said. “Boosting with a single vaccine dose in people with prior infection probably does. As new variants continue to emerge, it is important to fast track global rollout of vaccines to reduce transmission of the virus and remove the opportunities for new variants to arise.”
The authors noted in the study that the duration of immunity is unknown. “Durability of immunity to natural infection and following vaccination, as well as sustained vaccine efficacy and vaccine escape need to be monitored over time,” they wrote.
Apr 30 Science study
Apr 30 Imperial College London press release
Two B1351 COVID-19 variant clusters in Maryland detailed
In January and February, the Maryland Department of Health (MDH) reported a 17-person outbreak in which all four sequenced viruses were related strains of B1351, the variant first identified in South Africa. The cases mark the state’s first instance of non-travel–associated B1351, according to the Mortality & Morbidity Weekly Report late last week.
The outbreak consisted of two clusters and resulted in two hospitalizations and one death. According to investigators, the source patient was employed at an organization that had been reported through an anonymous tip line regarding COVID-19 safety concerns as several of the seven employees appeared to be in the workplace despite symptoms. Six of the employees, including the source patient, and five of their close contacts eventually received positive COVID-19 results.
Before the source patient had been diagnosed as having COVID, however, he or she went to an indoor, hours-long social gathering where masks were removed to eat. The six other people at the gathering tested positive for COVID 3 to 13 days after, but none of their close contacts were diagnosed as having the virus. (One of the people at the gathering was MDH’s original index case.)
Of the total 17 outbreak patients, 1 had been diagnosed as having COVID 5 months prior, and 2 had received the first dose of a two-dose COVID-19 vaccination 2 weeks before the likely exposure. None said they had contact with anyone connected with international travel. Viruses were sequenced from a close contact of the work cluster and three people from the indoor gathering.
“These first identified linked clusters of B.1.351 infections in the United States with no apparent link to international travel highlight the importance of expanding the scope and volume of genetic surveillance programs to identify variants, completing contact investigations for SARS-CoV-2 infections, and using universal prevention strategies, including vaccination, masking, and physical distancing, to control the spread of variants of concern,” write the authors.
Apr 30 MMWR study