SARS-CoV-2 Infection-Blocking Immunity Post Natural Infection: The Role of Vitamin D

Higher vitamin D levels before COVID-19 infection were significantly associated with protection against reinfection in the first 8 months after recovery, but this effect was not observed after 9-12 months and was not correlated with anti-spike protein antibody titers.

• In the first 8 months after recovery, those reinfected had a significantly higher incidence of low 25(OH)D levels (<30 ng/mL, 92% vs. 84.8%, p < 0.05); however, during the following three months, the incidence of low 25(OH)D levels was non-significantly higher among PCR-negative subjects compared to those reinfected (86% vs. 81.7, p = 0.15).  
• No significant difference in median anti-spike antibody titers was observed between the different 25(OH)D levels at all time intervals. The median anti-spike protein antibody titers tended to increase over time in the vitamin D-deficient group. 
• Multivariate analysis showed that age >44 years and anti-spike antibody titers >50 AU/mL were inversely associated with reinfection.  

10,132 adult members of a nation-wide health organization in Israel who had recovered from a documented COVID-19 infection.

• Patient vitamin D supplementation history was not available, the authors noted that in April 2020 the Health Ministry had recommended vitamin D supplements, which could have influenced vitamin D status.  
• Antibody levels were only available for a subset of participants. The time between sample collection and COVID-19 infection varied between subjects and may not provide an accurate picture of changes in antibody levels over time.  

The current study emphasizes the potential impact of pre-infection levels of vitamin D on reinfection during convalescence and the limitation of the immunoglobulins titer to serve as a stand-alone criterion to predict protective immunity against COVID-19. Higher pre-infection 25(OH)D level correlated with protective COVID-19 immunity during the first 8 months following COVID-19 infection, which could not be explained by anti-spike protein antibody titers. This effect dissipated beyond this period, demonstrating a biphasic 25(OH)D association that warrants future studies.

• This retrospective study examined the association between baseline 25(OH)D levels and reinfection rate and anti-spike protein antibody titer following COVID-19 infection. 
• The study population included 10,132 members of the Leumit Health Service HMO, aged 18 years or older, who met the following criteria: 1) had recovered from a documented COVID-19 infection between 1 February 2020 to 30 January 2022, in the absence of prior vaccination, 2) had at least one plasma 25(OH)D measurement prior to infection and recruitment, and 3) underwent RT-PCR testing for SARS-CoV-2 ≥ 3 months after recovery, and before booster injection if any. 

Abu Fanne R, Moed M, Kedem A, Lidawi G, Maraga E, Mohsen F, Roguin A, Meisel SR. SARS-CoV-2 Infection-Blocking Immunity Post Natural Infection: The Role of Vitamin D. Vaccines (Basel). 2023 Feb 17;11(2):475. doi: 10.3390/vaccines11020475.