Recommendation for the gap between two doses of COVID-19 vaccine

Bangladesh Health Watch is a civil society body. It is composed of individuals with illustrious backgrounds in public health.One of its technical committees is exclusively working on the different issues related to COVID-19 vaccination in the country and is headed by Dr A M Zakir Hussain, a former Director of Primary Health Care and Disease Control, Government of Bangladesh and former Regional Advisor for Regional Office for South-East Asia (SEARO), World Health Organisation (WHO).

Based on our detailed review of the scientific basis of the Oxford – AstraZeneca vaccine, as reported in reputed global journals, we would like to propose the Government of Bangladesh to kindly consider the adoption of a gap of 12 weeks (or 3 months) between the two doses of the said vaccine, instead of 8 weeks (or 2 months) as has been decided for now. The following is the rationale for our recommendation.

1. The Lancet published a paper of 71 scientists which found that in the participants who received two standard doses of the said vaccine, efficacy was higher in those with a longer prime-boost interval (vaccine efficacy 81.3% at ≥ 12 weeks gap, than 55.1% in whom vaccine gap was less than 6 weeks).

2. A review paper in the British Medical Journal based on 17,177 vaccinated people in the United Kingdom, Brazil and South Africa, support the British Government's approach of leaving 3 months gap between the two doses of the vaccine. A single standard dose of the vaccine was noted to provide 76% protection against symptomatic COVID-19 in the first 90 days after vaccination. This is in line with the previous research that found greater efficacy with longer intervals with vaccines like influenza and ebola (which are also RNA viruses).

3. 21 scientists in the USA found that spike-specific memory B lymphocyte cells (B type white blood cells, which produce antibody) were more abundant at 6 months than at 1-month post-infection (akin to a dose of vaccination). SARS-CoV-2- specific CD4+ T lymphocyte cells (T type white blood cells or helper cells, which activate B cells to produce antibody) and CD8+ T lymphocyte cells (T type white blood cells, which act as cytotoxic cells, i.e. kill infected cells) declined with a half-life of 3-5 months, indicating that a booster, i.e., the second dose of vaccine would work better if given at this half lifetime (i.e. 3 months). This paper was published in the prestigious journal 'Science'.

4. The three-month gap is a better strategy as more people can be protected more quickly, as even with one dose, people may reduce their risk of getting severely infected and also reduce their transmissibility.

Based on the above scientific justifications and based on discussion with selected key scientists in the country, the technical committee of Bangladesh Health Watch urges to kindly consider the three-month gap between the two doses of Oxford – AstraZeneca vaccine in Bangladesh.

Dr Mushtaque Chowdhury is the Convener of Bangladesh Health Watch.