Do your patients think that getting COVID-19 is totally protective against subsequent reinfection? Explain this to the Marines.
A study of U.S. marine recruits on their way to the starting camp on Parris Island, SC, showed that those who were HIV-positive at baseline, indicating prior exposure to SARS-CoV-2, maintained a certain risk of reinfection. They had about one-fifth the risk of subsequent infection, compared with seronegative recruits during basic training, but reinfections occurred.
“Although antibodies induced by the initial infection are largely protective, they do not guarantee effective SARS-CoV-2 neutralizing activity or immunity to subsequent infection,” they wrote.
An infectious disease specialist who did not participate in the study said the findings provide additional evidence on the level of immunity acquired after an infection.
“It’s clear that reinfections are occurring, which are important to public health and are something we need to keep in mind when advising patients on whether a previous infection protects them from reinfection.” Mark Siedner, MD, Said MPH, a clinician and researcher in the Division of Infectious Diseases at Massachusetts General Hospital, Boston, in an interview.
The results of the study reinforce that “not all antibodies are the same,” said Sachin Gupta, MD, an assistant physician in pulmonary medicine and critical care at the Alameda Health System in Oakland, California. “We are still seeing that 10% of people who have antibodies can become infected again,” he said in an interview.
Sealfon and colleagues presented a data analysis of the prospective CHARM study (COVID-19 Health Action Response for Marines).
CHARM included U.S. Marine recruits, mostly men, ages 18 to 20, who were ordered to follow an unsupervised quarantine for two weeks at home, after which they were presented at a facility. supervised by the Navy for an additional forty weeks.
At baseline, participants tested for seropositivity of SARS-CoV-2 immunoglobulin G (IgG), defined as a dilution of 1: 150 or more in the receptor-binding domain and the immunosorbent assay. bound to an enzyme bound to the full tip protein (ELISA).
Recruits completed questionnaires to ask them to report any of the 14 specific symptoms related to COVID-19 or any other unspecified symptoms, as well as demographic information, risk factors, and a brief medical history.
The researchers tested recruits for SARS-CoV-2 infection by polymerase chain reaction (PCR) assay at weeks 0, 1, and 2 of quarantine, and ruled out anyone with positive PCR results during the quarantine.
Participants who had three negative PCR results during quarantine and a baseline serology test at the beginning of the supervised quarantine period (either seronegative or seropositive) continued to enjoy their basic training at Marine Corps Recruit Depot, Parris Island , SC
Participants were prospectively followed by PCR tests at weeks 2, 4, and 6 in both the HIV-positive and seronegative groups, and serums were obtained at the same time.
Holes in immunological armor
Complete data were available for a total of 189 HIV-positive and 2,247 HIV-negative participants at enrollment.
In total, 19 of 189 HIV-positive recruits (10%) had at least one positive PCR test for SARS-CoV-2 infection during the 6-week follow-up period. This resulted in an incidence of 1.1 cases per person-year.
Of the 2,247 seronegative participants at baseline, 1,079 tested positive (6.2 cases per person-year; incidence rate 0.18).
Antibodies appeared to provide some protection to HIV-positive recruits, as evidenced by a higher likelihood of infection among those with lower full-length tip protein IgG titers than those with higher baseline titers (risk ratio 0.4 , Pg <.001).
Among seropositive participants who acquired a second SARS-CoV-2 infection, viral loads in medium-turbine nasal buffers were approximately 10-fold lower than those of seronegative recruits who acquired infections during follow-up.
“This finding suggests that some reinfected individuals may have a similar ability to transmit the infection than those first infected. The rate of reinfection after vaccines and natural immunity is important in estimating the proportion of vaccinated population to suppress the pandemic. “, the researchers wrote.
Baseline neutralizing antibody titers were detected in 45 of the first 54 seropositive recruits who remained PCR negative during follow-up, but also in 6 of 19 seropositive participants who became infected during the 6 weeks of observation.
Both Siedner and Gupta agreed with the authors that the risks of reinfection observed in young people and in physical form may differ for other populations, such as women (only 10% of HIV-positive recruits and 8% of seronegative recruits were women). ), elderly patients, or those who are immunocompromised.
Given that the adjusted probability ratio for reinfection in this study was almost identical to that of recent British study Sealfon and colleagues can compare infection rates among HIV-positive and seronegative health workers, the risk of reinfection for other young adults, and for the general population.
Added to the challenge of achieving herd immunity is the observation that some patients who have recovered from COVID-19 are skeptical about the need for additional protection.
“There are patients who feel that vaccination benefits them little, and I think they are the same people who would hesitate to get the vaccine anyway,” Gupta said.
While no vaccine is perfect: the failure rate of Moderna and Pfizer / BioNTech’s mRNA-based vaccines is about 5 percent, the protections they offer are unmistakable, Siedner said.
“I think it’s important to distinguish that most post-vaccine infections have been very mild,” he said. “In people with normal immune systems, we have not seen an attack of post-vaccine infections that require hospitalization. Even if people become infected after vaccination, vaccines protect people from a serious infection and that is what we want them to do it. “
The researchers stated: “Young adults, a high proportion of whom are asymptomatically infected and become HIV-positive in the absence of known infection, may be an important source of transmission to more vulnerable populations. Assessing protection against subsequent SARS-infection CoV-2 conferred by seropositivity in young adults is important in determining the need to vaccinate previously infected individuals in this age group. “
The study was funded by the Defense Health Agency and the Defense Advanced Research Projects Agency. Sealfon, Siedner and Gupta have no conflicts of interest to report. Gupta is a member of the editorial advisory board of this publication.
This article originally appeared on MDedge.com, which is part of the Medscape professional network.