We evaluated effectiveness of personal protective measures against severe acute respiratory disease coronavirus 2 (SARS-CoV-2) infection. Our case-control study included 211 cases of coronavirus disease (COVID-19) and 839 controls in Thailand. Cases were defined as asymptomatic contacts of COVID-19 patients who later tested positive for SARS-CoV-2; controls were asymptomatic contacts who never tested positive. Wearing masks all the time during contact was independently associated with lower risk for SARS-CoV-2 infection compared with not wearing masks; wearing a mask sometimes during contact did not lower infection risk. We found the type of mask worn was not independently associated with infection and that contacts who always wore masks were more likely to practice social distancing. Maintaining > 1 m distance from a person with COVID-19, having close contact for < 15 minutes, and frequent handwashing were independently associated with lower risk for infection. Our findings support consistent wearing of masks, handwashing, and social distancing to protect against COVID-19.

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Background. Effectiveness of personal protective measure against COVID-19 infection is largely unknown. Methods. We conducted a retrospective case-control study, using a cohort of contact tracing records in Thailand. A total of 1,050 asymptomatic contacts of COVID-19 patients between 1 and 31 March 2020 were retrospectively interviewed by phone about their protective measures against COVID-19 infection. Cases were defined as asymptomatic contacts who were diagnosed with COVID-19 by 21 April 2020. Multilevel mixed-effect logistic regression models were used Findings. Overall, 211 (20%) were diagnosed with COVID-19 by 21 Apr 2020 (case group) while 839 (80%) were not (control group). Fourteen percent of cases (29/210) and 24% of controls (198/823) reported wearing either non-medical or medical masks all the time during the contact period. Wearing masks all the time (adjusted odds ratio [aOR] 0.23; 95%CI 0.09-0.60) was independently associated with lower risk of COVID-19 infection compared to not wearing masks, while wearing masks sometimes (aOR 0.87; 95%CI 0.41-1.84) was not. Shortest distance of contact >1 meter (aOR 0.15; 95%CI 0.04-0.63), duration of close contact ≤15 minutes (aOR 0.24; 95%CI 0.07-0.90) and washing hands often (aOR 0.33; 95%CI 0.13-0.87) were significantly associated with lower risk of infection. Sharing a cigarette (aOR 3.47; 95%CI 1.09-11.02) was associated with higher risk of infection. Those who wore masks all the time were more likely to wash hands and practice social distancing. We estimated that if everyone wore a mask all the time, washed hands often, did not share a dish, cup or cigarette, maintained distances >1 meter and spent ≤15 minutes with close contacts, cases would have been reduced by 84%. Interpretation. Our findings support consistently wearing masks, washing hands, and social distancing in public to protect against COVID-19 infections. Combining measures could substantially reduce infections in Thailand.

Objective: On 1 December 2020, the Department of Disease Control of Thailand was notified of a cluster of food poisoning cases among participants at a church festival in Mae Ai district, Chiang Mai province. We conducted an outbreak investigation to confirm diagnosis, describe the epidemiological characteristics of the outbreak, identify possible sources of the outbreak and provide appropriate control measures. Methods:We reviewed medical records of the food poisoning cases from the health care centres. Active case finding was conducted among participants who had consumed food and water at the festival. An environmental survey was done in the village where the festival was held. A case-control study was conducted to identify the source of the outbreak. Samples for laboratory analysis included rectal swabs and fresh stool specimens from the cases and food handlers, surface swabs of cooking equipment, food, water and ice samples.Results: Among 436 participants surveyed, 368 (84.4%) cases of food poisoning were identified. The most common clinical manifestation was abdominal pain (89.7%), followed by watery diarrhoea (45.7%), nausea (43.5%), vomiting (38.9%), fever (18.5%) and bloody diarrhoea (4.6%). None died in this outbreak. The case-control study showed that mixed spicy seafood salad served in the festival was significantly associated with the disease by both univariable and multivariable analyses. However, the causative agent could not be identified. The environmental investigation suggested this seafood might have been undercooked. Conclusion:Clinical manifestations of the cases, incubation period and the suspected seafood salad suggested seafood-related food poisoning. Grimontia hollisae, the organism causing illness similar to Vibrio parahaemolyticus and commonly undetectable in the laboratory with routine testing, might be the pathogen that caused this outbreak.G. hollisae should be in differential diagnosis and identified in seafood-associated outbreaks.

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ObjectiveDespite implementing hepatitis B immunoglobulin (HBIG) and vaccination, data suggest it would not be sufficient to reach the elimination targets. Tenofovir disoproxil fumarate (TDF) has been added to the Thai national standards of care for prevention of transmission of the hepatitis B virus during birth. To optimise national strategies in Thailand, we assessed TDF’s effectiveness for prevention of mother-to-child transmission and conducted cost-effectiveness analyses of different TDF-based strategies.Research design and methodsWe retrospectively reviewed medical records of mother and infant pairs whose mothers were positive for hepatitis B e-antigen (HBeAg) and received TDF to prevent maternal transmission of viral hepatitis B during 2018–2020. Based on the available data on transmission rate, we also applied a decision tree to estimate the cost-effectiveness of different TDF-based strategies to eligible mothers. These included: (1) HBIG for all hepatitis B virus (HBV) exposed infants; (2) HBIG for only infants of HBeAg-positive mothers (‘HBIG for e-positive’) and (3) without HBIG to infants (‘HBIG-free’). The incremental cost-effectiveness ratio between the different strategies and baseline intervention without TDF was calculated. The one-way sensitivity analysis was used to adjust prevalence of HBeAg-positive mothers, cost of HBIG, cost of TDF and transmission rate.ResultsOf 223 infants enrolled, 212 (95.0%) received HBIG, while 11 (5.0%) did not. None of the infants had chronic HBV infection. The most cost-saving intervention was ‘HBIG-free’ followed by ‘HBIG for e-positive’. The one-way sensitivity demonstrated that the results were reasonably robust to changes. The cost-saving was greater with a higher hepatitis B virus surface antigen (HBsAg) prevalence. The HBIG-free strategy remained best at 0%–1.4% transmission rates, meeting the additional target for eliminations.ConclusionThe study is the first cost-effectiveness analyses to provide evidence supporting an HBIG-free strategy in an antiviral era. This approach should be considered to prevent mother-to-child transmission in resource-constrained settings, particularly in countries with a high HBsAg prevalence.

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