In a recent article published in Lancet Infectious Diseases, researchers performed a scientific review and meta-regression study to find out the breadth and duration of the protective immunity conferred by previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and hybrid immunity. They evaluated this data evidence against SARS-CoV-2 Omicron-caused infection.

Study: Protective effectiveness of previous SARS-CoV-2 infection and hybrid immunity against the omicron variant and severe disease: a scientific review and meta-regression. Image Credit: CI Photos/Shutterstock

Background

Nearly all of the worldwide population developed hybrid immunity post mass vaccination drives, followed by the appearance of the SARS-CoV-2 Omicron (B.1.1.529) variant that caused reinfections as a result of its immune-evading potential.

Concerning the study

For the current study, researchers searched several databases, including MEDLINE, European PubMed Central, and clinicaltrials.gov, to call a number of, for the period between January 1, 2020, and June 1, 2022. They searched cohort, case-control, and cross-sectional studies using keywords related to SARS-CoV-2, its prior infection, reinfection, presence of antibodies, and hybrid immunity. 

The researchers assessed several outcomes related to hybrid immunity, akin to hybrid immunity relative to previous infection alone, vaccination alone, and hybrid immunity with fewer vaccine doses. In addition they determined the chance of bias within the studies covered within the study evaluation. Moreover, they used log-odds random-effects meta-regression to estimate the breadth of immune protection against Omicron at one-month intervals throughout the study duration.

The analyses covered studies examining immune protection against Omicron reinfection through which the exposure group comprised individuals with prior infection with any SARS-CoV-2 variant or hybrid immunity. The control group had immune-naive, previously infected, or vaccinated individuals. The researchers determined Omicron infection by whole genomic sequencing or based on dominance periods of the variants per the Global Initiative on Sharing Avian Influenza Data (GISAID) database.

Study findings

Each previous SARS-CoV-2 infection and hybrid immunity conferred adequate protection against Omicron infection(s), nevertheless it waned quickly. Furthermore, a previous episode of COVID-19 provided higher and more persistent protection against hospitalization or severe COVID-19 than only vaccination. Conversely, individuals with hybrid immunity exhibited more durable protection against all COVID-19 outcomes, emphasizing the importance of vaccinating previously infected individuals.

Since infection-induced protection against breakthrough infection wanes quickly and vaccination upturns the sturdiness of this protection; due to this fact, vaccination is a reliable intervention to thwart severe COVID-19 outcomes and reduce post-COVID-19 complications, including cardiovascular and neurological sequelae.

Moreover, the study results highlighted the necessity for optimally timing the first COVID-19 vaccination series and the booster doses for people. As is already known, boosting time varies for a person previously infected with SARS-CoV-2 or who had a breakthrough infection after the start of the first COVID-19 vaccination series in comparison with an immune-naïve individual. It is affordable to delay boosting by six months because individuals with a previous infection and fully vaccinated individuals naturally enjoy higher immunity against severe COVID-19.

More importantly, the researchers advocated conducting serosurveys for estimating population-level prior infection-induced seroprevalence. It’s so because the best variety of vaccine doses and the interval between doses mostly differ for various settings on the population level. This must be the premise for national vaccination policies in lots of countries, especially those not using inactivated COVID-19 vaccines. One other example might be countries that only used SARS-CoV-2 spike (S)-protein-based vaccines.

In such countries, they might discover individuals as infected before with an anti-nucleocapsid diagnostic assay to tell recommendations for boosters. This approach, nonetheless, doesn’t apply to high-risk groups (e.g., immunocompromised individuals).

The authors cautioned that modifications to COVID-19 vaccination programs might diminish vaccine uptake. So, it’s best to maintain vaccine rollout easy. Moreover, the World Health Organization (WHO) has advisable not delaying or excluding individuals from vaccination as a result of past infections. As well as, boosting could be helpful before periods of increased COVID-19 incidence, akin to in winter, especially when the SARS-CoV-2 variant that caused the past infection is unknown. As is widely known, the prevalence of COVID-19 stays highly underestimated in most countries throughout the pandemic.

Conclusions

The study findings clarified the substantial durability of hybrid immunity that would help inform the timing of vaccination programs in populations with higher past SARS-CoV-2 infection rates.

Future studies should assess the protective effect of hybrid immunity against hospitalization or severe disease because these two outcomes drive most COVID-19 policy decisions. Thus, it’s crucial to know the way much the hybrid immunity-induced immunity wanes over a chronic duration, particularly amid the appearance of recent SARS-CoV-2 variants of concern. Such precise quantification of the sturdiness of this protection could help inform the necessity and timing of booster vaccinations.

Journal reference:

• Niklas Bobrovitz, Harriet Ware, Xiaomeng Ma, Zihan Li, Reza Hosseini, Christian Cao, Anabel Selemon, Mairead Whelan, Zahra Premji, Hanane Issa, Brianna Cheng, Laith J Abu Raddad, David L Buckeridge, Maria D Van Kerkhove, Vanessa Piechotta, Melissa M Higdon, Annelies Wilder-Smith, Isabel Bergeri, Daniel R Feikin, Rahul K Arora, Minal K Patel, Lorenzo Subissi. (2023). Protective effectiveness of previous SARS-CoV-2 infection and hybrid immunity against the omicron variant and severe disease: a scientific review and meta-regression. Lancet Infectious Diseases. doi: https://doi.org/10.1016/S1473-3099(22)00801-https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(22)00801-5/fulltext