Role of booster vaccines and hybrid immunity against severe COVID-19 outcomes during BA.5 omicron predominance in Thailand

Owing to both vaccine- and infection-induced immunity, the COVID-19 seroprevalence is ~90% in most countries. It is important to examine the protective role of booster vaccines and hybrid immunity in the COVID-endemic state. Utilizing a hospital information system for COVID-19, we conducted a cohort study by linking laboratory-confirmed COVID-19 case data to the national immunization records during the BA.5 omicron predominant period (1 August-31 December 2022) in Chiang Mai, Thailand. Out of 63,009 adults with COVID-19 included in the study, there were 125 (0.2%) severe COVID outcomes and 6.4% had a previous omicron infection. Protection against severe COVID-19 was highest among those with at least one booster vaccine (63%; aHR 0.37 [95%CI 0.19-0.73]) as compared to those without prior vaccination or natural infection. Hybrid immunity offered better protection (35%; aHR 0.65 [95%CI 0.09-4.73) than primary vaccine series alone or previous infection alone. Evaluating risk by age group, those aged 70 years or more had nearly 40 times (aHR 39.58 [95%CI 18.92-82.79]) the risk of severe-COVID-19 as compared to the 18-39-year age group. While booster vaccines remain the most effective way of protecting against severe COVID-19, particularly in the elderly, hybrid immunity may offer additional benefit.

Heterologous booster vaccines reduce severity and mortality in COVID-19 during BA.2 and BA.4/BA.5 omicron predominance in Thailand

BACKGROUND

The COVID-19 pandemic has evolved quickly, with variants of concern resulting in the need to offer booster vaccinations. Unfortunately, the booster uptake has been slow and vaccine response has shown to wane over time. Therefore, it's critical to evaluate the role of vaccinations on outcomes with newer sub-lineages of omicron.

METHODS

Utilising a Hospital Information System established in Chiang Mai, Thailand, we conducted a cohort study by linking patient-level data of laboratory-confirmed COVID-19 cases to the national immunization records, during BA.2 and BA.4/BA.5 predominance.

RESULTS

In adjusted cox-proportional hazard models, BA.4/BA.5 was not associated with more severe COVID-19 outcomes or deaths as compared to BA.2. Risk of severe outcomes and deaths were significantly reduced with third (87% and 95%) and fourth (88% and 95%) dose vaccination, while events were not observed with a fifth dose. Across the regimens, vaccination within 14-90 days prior showed the highest level of protection. All the vaccine types used for boosting in Thailand offered similar protection against severe COVID-19.

CONCLUSIONS

Boosters provide high level of protection against severe COVID-19 outcomes and deaths with newer omicron sub-lineages. Booster campaigns should focus on improving coverage utilising all available vaccines to ensure optimal protection.

Waning vaccine response to severe COVID-19 outcomes during omicron predominance in Thailand

BACKGROUND

The COVID-19 pandemic has evolved quickly, with different variants of concern resulting in the need to offer continued protection through booster vaccinations. The duration of enhanced protection with booster doses against severe COVID-19 is still unclear. Understanding this is critical to recommendations on the frequency of future booster doses.

METHODS

Utilising a Hospital Information System for COVID-19 established in Chiang Mai, Thailand, we conducted a cohort study by linking patient-level data of laboratory-confirmed COVID-19 cases to the national immunization records, during the omicron predominant period (1 February- 31 July 2022).

RESULTS

Out of 261,103 adults with COVID-19 included in the study, there were 333 (0.13%) severe COVID-19 cases and 190 (0.07%) deaths. Protection against severe COVID-19 was highest with boosters received >14-60 days prior to positive test (93%) and persisted at >60-120 days (91%) but started to wane at >120-180 days (77%) and further at >180 days (68%). The rate of waning differed with age. Those ≥70 years showed faster waning of booster vaccine responses as compared to those aged 18-49 years, who retained good responses up to 180 days. Equivalent risk reduction against severe COVID-19 was seen with all the vaccine types used as boosters in Thailand.

CONCLUSIONS

Booster doses provided high levels of protection against severe COVID-19 with omicron, up to 4 months. Repeat boosters will be required to continue protection beyond 4 months, particularly in the elderly. mRNA and viral vector vaccines can be used flexibly to improve booster coverage.

Effectiveness of heterologous third and fourth dose COVID-19 vaccine schedules for SARS-CoV-2 infection during delta and omicron predominance in Thailand: a test-negative, case-control study

Background

The Coronavirus disease 2019 (COVID-19) pandemic has evolved quickly, with numerous waves of different variants of concern resulting in the need for countries to offer continued protection through booster vaccination. To ensure adequate vaccination coverage, Thailand has proactively adopted heterologous vaccination schedules. While randomised controlled trials have assessed homologous schedules in detail, limited data has been reported for heterologous vaccine effectiveness (VE).

Methods

Utilising a unique active surveillance network established in Chiang Mai, Northern Thailand, we conducted a test-negative case control study to assess the VE of heterologous third and fourth dose schedules against SARS-CoV-2 infection among suspect-cases during Oct 1-Dec 31, 2021 (delta-predominant) and Feb 1-Apr 10, 2022 (omicron-predominant) periods.

Findings

After a third dose, effectiveness against delta infection was high (adjusted VE 97%, 95% CI 94-99%) in comparison to moderate protection against omicron (adjusted VE 31%, 95% CI 26-36%). Good protection was observed after a fourth dose (adjusted VE 75%, 95% CI 71-80%). VE was consistent across age groups for both delta and omicron infection. The VE of third or fourth doses against omicron infection were equivalent for the three main vaccines used for boosting in Thailand, suggesting coverage, rather than vaccine type is a much stronger predictor of protection.

Interpretation

Appropriately timed booster doses have a high probability of preventing COVID-19 infection with both delta and omicron variants. Our evidence supports the need for ongoing national efforts to increase population coverage of booster doses.

Funding

This research was supported by the National Research Council of Thailand (NRCT) under The Smart Emergency Care Services Integration (SECSI) project to Faculty of Public Health Chiang Mai University.

Reduction in severity and mortality in COVID-19 patients owing to heterologous third and fourth-dose vaccines during the periods of delta and omicron predominance in Thailand

OBJECTIVES

The COVID-19 pandemic has evolved quickly, with different variants of concern resulting in the need for countries to offer booster vaccinations. Although studies have assessed homologous schedules in detail, the effectiveness of heterologous booster vaccine schedules against severity and mortality with newer variants remains to be explored fully.

METHODS

Utilizing a Hospital Information System for COVID-19 established in Chiang Mai, Thailand, we conducted a cohort study by linking patient-level data on laboratory-confirmed COVID-19 cases to the national immunization records, during delta-predominant and omicron-predominant periods.

RESULTS

Compared to omicron, COVID-19 cases during the delta period were 10 times more likely to have severe outcomes and in-hospital deaths. During omicron, a third vaccine dose had an 89% reduced risk of both severe COVID-19 and death. The third dose received 14-90 days before the date of the positive test showed the highest protection (93%). Severe outcomes were not observed with the third dose during delta, and the fourth dose during the omicron period. All the vaccine types used for boosting in Thailand offered similar protection against severe COVID-19.

CONCLUSION

Booster doses provided a very high level of protection against severe COVID-19 outcomes and deaths. Booster campaigns should focus on improving coverage by utilizing all available vaccines to ensure optimal protection.

Mental health circumstances among health care workers and general public under the pandemic situation of COVID-19 (HOME-COVID-19)

BACKGROUND

After the spread of the coronavirus disease 2019 (COVID-19) globally, upgraded quarantine and physical distancing strategy, strict infection measures, and government's strict lockdown have been abided to confront the spread of the COVID-19 in Thailand. During the COVID-19 pandemic, concerns about the mental health and psychosocial problems among health care workers and the general population are now arising. Yet, information on mental health and psychosocial problems among health care workers and the general population have not been comprehensively reported in Thailand. As such, we conduct a cross-sectional study, a national online survey to describe the short- and long-term consequences of the COVID-19 pandemic on mental health and psychosocial problems among health care workers and the general population in Thailand.

METHODS

This study is a repeated cross-sectional study, an open online voluntary national-based survey during the wave I (April 21-May 4, 2020) follow-up in the wave II (August 3-16, 2020), wave III (November 15-28, 2020), and a 1-year follow-up survey (wave IV: April 21-May 4, 2021) in Thailand. Health care workers at the hospitals and the adult general population will be invited to participate in the online survey via the SurveyMonkey that limits one-time participation per unique internet protocol address. The target sample size of at least 1182 health care workers and 1310 general populations will be required to complete the online survey for each wave of the survey. Sociodemographic characteristics and a set of measurement tools for mental and psychosocial problems for each subcohort including depression, anxiety, stress, resilient copings, neuroticism, perceived social support, wellbeing, somatic symptoms, insomnia, burnout (for healthcare workers), and public stigma toward COVID-19 infection (for the general population) will be collected. For all estimates of prevalence, we will weigh data for all wave analyses under the complex design of the survey. Subgroup analyses stratified by key characteristics will also be done to analyze the proportion differences. For the repeated cross-sectional survey, we will combine the data from the wave I to wave IV survey to analyze changes in the mental health status. We will perform multilevel logistic regression models with random intercepts to explore associations with individual-level and region-level/hospital-level predictors. We also plan to perform an ancillary systematic review and meta-analysis by incorporating data from our findings to all available evidence.

RESULTS

Our findings will provide information on the short- and long-term mental health status as well as the psychosocial responses to the COVID-19 outbreak in a national sample of health care workers and the general population in Thailand.

CONCLUSION

This prospective, nationally based, a repeated cross-sectional study will describe the mental health status and psychosocial problems among health care workers and the general population in Thailand during the COVID-19 pandemic.

ETHICS AND DISSEMINATION

Ethical approval for the study was obtained from the Faculty of Public Health and Faculty of Pharmacy, Chiang Mai University. The findings will be disseminated through public, scientific, and professional meetings, and publications in peer-reviewed journals.

THAI CLINICAL TRIALS REGISTRY (TCTR) REGISTRATION NUMBER

TCTR20200425001.