Additionally, contrary to predictions, they discovered that previously infected obese patients had a stronger and longer-lasting immune response.
New study reveals that, while the number of SARS-CoV-2 antibodies decrease over time in both previously infected and vaccinated patients, antibody performance improves only after previous infection (and not vaccination). This could explain why people who have been previously infected seem to be better protected against a new infection than those who have merely been vaccinated.
Dr. Carmit Cohen of the Sheba Medical Center in Ramat Gan, Israel, and colleagues also discovered that previously infected obese patients had a stronger and longer-lasting immune response than overweight and normal-weight patients, contrary to predictions.
While SARS-CoV-2 recovered patients remain protected against re-infection for a long period, breakthrough infections are more common six months following immunization. The authors of this study evaluated the humoral (antibody-induced) immune response in COVID-19 recovered but unvaccinated individuals for up to a year to those who had received two doses of the Pfizer vaccine (but had not previously been infected) over an eight-month period.
The study enrolled previously infected-unvaccinated and double-vaccinated-never infected people from March 25 to November 25, 2020, and finished in April 2021, just before the delta variant arrived in Israel. Those previously afflicted in this study were infected with the original and alpha forms (and in some cases, beta) of SARS-CoV-2, albeit the exact variant used to infect each patient is unknown due to the laboratory’s inability to sequence variants until well after the study began.
PCR testing was used to track 130 patients who had been diagnosed with SARS-COV-2. These patients had not been vaccinated prior to the trial and remained unvaccinated throughout. During the course of the trial, none of these patients became infected again. Acute (during infection and immediately after) and long-term (beyond 6 weeks) symptoms were recorded. They compared the anti-spike protein IgG and neutralising antibodies of these 130 recovered patients to 402 age and BMI-matched people who had never had COVID-19 but were double-vaccinated with the Pfizer vaccine. These double-vaccinated patients remained uninfected throughout the study; however, evidence had begun to emerge in Israel at this time (second quarter of 2021) that double-vaccinated, never infected healthcare workers were experiencing ‘breakthrough’ infections six months after their second dose, whereas previously infected individuals who had not been vaccinated were not being reinfected. The goal of this research was to find out why.
For sub-cohorts made up of 16 people who had recovered from COVID-19 and 22 never-infected individuals who had been twice vaccinated, the avidity index (simply described as the quality of antibody performance) was compared at one and six months. Questionnaires on symptoms, particularly long COVID, were also obtained from recovered patients.
The researchers discovered that the number of antibodies a month after immunization was higher than in the COVID-19 recovered patients. The vaccinated group, on the other hand, saw a steeper reduction in these figures. Initially, the avidity (quality of antibody performance) score was higher in vaccinated persons than in recovered patients. However, up to six months after vaccination, avidity in vaccinated persons did not alter appreciably, whereas it gradually rose in recovered patients, perhaps protecting them from reinfection.
Surprisingly, and contrary to expectations, the level (titers) of antibodies in recovered patients with a BMI of 30 or higher (in the obese range) were higher at all time points when compared to those with a BMI of 30 or less (normal weight to overweight range), implying that people with obesity who had previously been infected were better protected against future infection than those who were overweight or normal weight and had previously been infected.
42 (36 percent) of all recovered patients had long-term COVID symptoms, including mental health (5 percent), neurological (9 percent), cardiovascular (5 percent), and respiratory (31 percent) manifestations.
The study, to be presented at this year’s European Congress of Clinical Microbiology & Infectious Disease, concluded: “While the number of antibodies decrease with time in both COVID-19 recovered (but never vaccinated) patients and vaccinated (but never infected) individuals, the quality of antibodies increases following infection but not after vaccination. People with obesity have a significantly higher and sustained antibody-induced immune response following infection. These results provide specific characteristics of the immune response that may explain the differential protection against COVID-19 in previously infected compared with only-vaccinated individuals.”
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