On this Australia Day (26/1) exactly 39 years ago I came to Australia as a refugee. It has been a long and winding journey, but I have survived and made meaningful contributions to this beautiful country that I call home. On 26/1 people are talking about ‘invasion day’, but I am talking about a personal Thanksgiving day. My story started with a hilarious interview in Songkhla Refugee Camp (Thailand) 40 years ago.

Leaving Vietnam

On April 16, 1981, my elder brother, my sister, I and 20 friends left Vietnam in a wooden fishing boat heading toward Thailand. Some friends were…

Norwegian health authority reported that 33 people had died after receiving the first dose of Pfizer-BioNTech Covid-19 vaccine [1]. The news has generated concern and even fear among the general community. However, my evaluation suggests that the fear is not founded.

It is hard to make sense out of the 33 deaths without knowing the number of vaccinated people. According to The Age, Norway has vaccinated approximately 42,000 elderly people, mostly in nursing homes. Thus, the one-week risk of mortality is 0.078%.

Is the 0.078% risk too high? No. In a study published in PLoS ONE, the investigators followed 690…

Australian experts are debating about the efficacy of AstraZeneca vaccine. Some argue that the efficacy (VE) of the vaccine is not good enough for herd immunity; others say that it is better than … face mask. I think the debate has been misled by the heavy reliance on the average. In this note, I want to make 3 comments on the true value of VE and its implication for herd immunity.

Australia is about to implement a COVID-19 vaccine program, with Oxford/AstraZeneca vaccine being the intervention of choice. It is expected that up to 80,000 people will be vaccinated by…

The 2020 Vietnam’s beauty contest has concluded, and Miss Đỗ Thị Hà has been crowned Miss Vietnam 2020 [1]. The 19 yr old girl stands at a proud 175 cm tall, but her weight was only 55 kg. She and her fellow beauty contestants are classified as ‘underweight’.

I have over the years collected data pertaining to basic anthropometric parameters of Miss Vietnam titleholders. The data show that their height has increased over time. …

In the famous study, DANMASK, the authors conclude that wearing surgical mask together with social distancing practice did not reduce the risk of SARS-Cov-2 infection. However, using a Bayesian inference, I show that their result is consistent with a risk reduction of up to 28%.

Rarely a scientific study generates a lot of controversies, but that is the case for the DANMASK study [1]. In this study, the authors found that face mask wearing did not reduce the risk of infection with SARS-Cov-2 (odds ratio, 0.82; 95% CI, 0.54 to 1.23; P = 0.33) [1]. However, most newspapers and health…

Pfizer has just announced that their vaccine trial had concluded with an impressive result: 95% efficacy [1]. One does not need to do any fancy analysis to see that the efficacy is real. Here, I would like to offer a Bayesian interpretation of the efficacy.

Briefly, the trial has enrolled 43,661 volunteers, and as of 13/11/2020 41135 volunteers have received a second dose of the vaccine. Assuming that half the 41135 participants have been randomly assigned to the vaccine group, and the rest to placebo. According to the press release, 170 participants were infected with SARS-Cov-2, and among whom, only…

Vietnam is the 15th most populous country in the world. The country’s population is rapidly aging with significant changes in lifestyle and dietary habits. About 28% of women and 16% of men aged 50 and older are having osteoporosis, but most of them are undiagnosed and not treated.

Vietnam is a developing country, with per-capita GDP being around $2600 (2018 figure). Vietnam has a population of ~97 million, making it the 15th largest country in the world [1]. The country’s population is aging: at present the proportion of population aged 60 years and older is 12%, but this is expected…

The encouraging results of Pfizer’s vaccine against Covid-19 has renewed the idea of herd immunity. Central to the idea is the question “how many people in the general community need to be vaccinated to create herd immunity?” This note will answer that question.

By now, most people probably know what is herd immunity (also referred to as herd protection). Briefly, the idea of herd immunity is based on the conjecture that when a large proportion of people is immune to an infectious disease, these people will provide indirect protection to those not immune to the disease (see illustration). So, if…