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COVID-19 Evolving Evidence

OT&P Healthcare: Health Information You Can Trust

OT&P strongly advocate vaccination as a key factor in the control of the Covid pandemic. Our Covid public health resources have been widely shared with more than 1 million Chinese language views. Below is a summary of our analysis of important articles and evolving research along with original references.

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Public health experts in China argue that evidence supports 14-day quarantine for incoming travellers.

Public health experts describe their experience of quarantine in China. They state ‘some countries strengthened the controls of inbound passengers—for example, increasing quarantine from 14 days to 21 or even 28 days. Such extended quarantine measures are probably an over-reaction to the risk’.


  • Tu, H., Hu, K., Zhang, M., Zhuang, Y., & Song, T. (2021, December 2). Effectiveness of 14 Day Quarantine Strategy: Chinese Experience of Prevention and Control. The BMJ. Retrieved December 3, 2021, from
Ivermectin is not of benefit in Covid-19, except possibly marginal benefit in those who are co-infected with worms.

The story of Ivermectin is one of science, pseudoscience, politics and fraud. For anyone interested in the evidence, this is an excellent analysis.


Since 2013 Hong Kong has the world’s highest life expectancy at birth.

Hong Kong's leading longevity is the result of fewer diseases of poverty while suppressing the diseases of affluence. A unique combination of economic prosperity and low levels of smoking with development contributed to this achievement. As such, it offers a framework that could be replicated through deliberate policies in developing and developed populations globally.


  • Ni MY; Canudas-Romo V; Shi J; Flores FP; Chow MSC; Yao XI; Ho SY; Lam TH; Schooling CM; Lopez AD; Ezzati M; Leung GM; (n.d.). Understanding longevity in Hong Kong: A comparative study with long-living, high-income countries. The Lancet. Public Health. Retrieved November 22, 2021, from

Long term symptoms can impact half of all cases of Covid-19.

In this systematic review of 57 studies comprising more than 250,000 survivors of COVID-19 more than half had at least one long term sequelae after 6 months. Long Covid may be expected to place a significant burden on health systems in the future. We have collated a Long Covid Resource centre to pool information on this issue as the evidence evolves.


With Delta infection non vaccinated individuals are >11x more likely to die.

The CDC are now publishing evidence of age and vaccination status for both hospitalization and death. The data confirms the significant increase in risk associated with both age and lack of vaccination.


Quarantine balances the risk to the population with the freedom of an individual. What about the psychological and social impact on individuals?

A recent study in Hong Kong explored attitudes to quarantine in people who had been quarantined within the city. This study highlights the need for inclusiveness, reasonableness, openness and transparency when making decisions regarding quarantine measures in order to mitigate negative psychosocial consequences.


It is early in our understanding of the psychological and social impact of the Covid pandemic. Early evidence suggests the adverse effects to be greatest amongst women and the young.

The Covid pandemic has had an enormous impact on mental health, anxiety and depression. This study considers the evidence across 204 countries, and shows significant impact, especially among women and younger people.


Following vaccination immunity is falling against mild disease but protection against severe disease is holding up very well

In this study the vaccine efficacy against mild disease one month after vaccination was 88% by five months the efficacy had dropped to 47% which is consistent with studies showing a drop in antibody levels. However, the efficacy in preventing hospitalization remained high. 87% after 1 month and 88% after five months.


Which behaviours in lockdown predict positive and negative mental health?

Science is about testing assumptions and challenging alternative hypotheses. Sometimes the evidence is blindingly obvious. Gardening, exercise, listening to music, hobbies and reading are associated with positive outcomes. Following the news on Covid, social media and TV are associated with negative outcomes.


Further evidence that immunity is greater following natural infection than vaccination

Not only are natural antibody levels higher but they also elicit different pathway responses.


  • Anderson, E. M., Eilola, T., Goodwin, E., Bolton, M. J., Gouma, S., Goel, R. R., Painter, M. M., Apostolidis, S. A., Mathew, D., Dunbar, D., Fiore, D., Brock, A., Weaver, J. E., Millar, J. S., DerOhannessian, S., Unit, T. U. P. C. O. V. I. D. P., Greenplate, A. R., Frank, I., Rader, D. J., … Hensley, S. E. (2021, January 1). SARS-COV-2 infections elicit higher levels of original antigenic sin antibodies compared to SARS-COV-2 mrna vaccinations. medRxiv. Retrieved October 6, 2021, from
What can we learn from the Danish experience of Covid

Denmark has vaccinated 97% of the population over 60 and relaxed all public health measures. Cases are slowly rising in the younger population but the majority are mild. The academic world is watching Denmark to see what endemic Covid looks like.


Vaccination works very well but vaccination and previous Covid infection gives even greater protection.

In this excellent study of a prison population in the USA there was a significant outbreak of Delta infection. 80% of the population was already vaccinated and for this reason the majority of infections were in vaccinated individuals. However, 3 out of the 4 hospitalizations and the only death were in unvaccinated prisoners. The lowest attack rates were in people who had been vaccinated but also had prior Covid. This supports findings from a recent Israeli study on the higher levels of immunity from vaccination plus natural infection.


  • Centers for Disease Control and Prevention. (2021, September 23). Outbreak of SARS-CoV-2 B.1.617.2 (Delta) Variant Infections Among Incarcerated Persons in a Federal Prison — Texas, July–August 2021 Centers for Disease Control and Prevention. Retrieved September 27, 2021, from
Post vaccination Covid is a milder disease

This article in the Atlantic asks whether post-vaccination Covid is a different disease. We have very good evidence that mortality and complications are significantly less in individuals with prior infection or vaccination.


Living with Covid is the only possible long-term strategy and Hong Kong has much to learn from the experience of Singapore.

Public health communication involves an open and honest acceptance of uncertainty and discussion of choices as evidence evolves. In this discussion Prof Hsu said severe illness and deaths will rise as measures ease, but aiming for no deaths means the constraints on society will be extremely high: "We haven't talked about what we might want to accept in terms of the cost of living with Covid-19."


More evidence of the effectiveness of Covid vaccination

The UK reviewed all deaths from Covid between January and July 2021. There were 51,281 deaths in the period studied. There were 640 deaths in fully vaccinated individuals meaning that 98.8% of the deaths from Covid in this period occurred in people who were not fully vaccinated.


Longer periods between first and second dose of Covid vaccines produces a significantly better immune response.

Early in the pandemic a study of AstraZeneca showed a surprising result. Individuals given a lower dose of vaccine by mistake had a larger immune response. The UK subsequently made a public health decision to increase the time between the first and second doses in an attempt to give as many people as possible some immunity. We now have very good evidence that this was the correct decision. An important example of using evidence to guide public health decisions rather than making assumptions.


  • Flaxman A; Marchevsky NG; Jenkin D; Aboagye J; Aley PK; Angus B; Belij-Rammerstorfer S; Bibi S; Bittaye M; Cappuccini F; Cicconi P; Clutterbuck EA; Davies S; Dejnirattisai W; Dold C; Ewer KJ; Folegatti PM; Fowler J; Hill AVS; Kerridge S; Minassian AM; Mongkolsapaya J; Mujadidi. (n.d.). Reactogenicity and immunogenicity after a late second dose or a third dose of ChAdOx1 nCoV-19 in the UK: a substudy of two randomised controlled trials (COV001 and COV002). Lancet (London, England). Retrieved September 27, 2021, from

We will continue to update this timeline regularly to include major milestones and information. If you’d like to receive updates directly to your inbox, please subscribe to our newsletter.

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