Vaccination offers the best protection from COVID 19
BRGP opinion on covid vaccines.
NSW has been free of covid transmission for some months but there is a constant risk of reintroduction since hotel quarantine is not perfect and eventually international travel numbers will increase again. Widespread immunisation will mean that the public health response can effectively control the inevitable future outbreaks without resorting to lockdowns or border closures. At Brunker Rd General Practice we are keen to play a part in the immunisation campaign and recommend that all eligible patients take up the offer of covid vaccine.
How effective are the vaccines?
In trials the Oxford Astra-Zeneca vaccine we have available is 67% effective at preventing symptomatic covid, and 100%effective at preventing hospitalisation(1). The Pfizer mRNA vaccine was 95% effective at preventing symptomatic covid19 infection in its trials. While at first glance the Pfizer vaccine has higher numbers this does not necessarily make it a better vaccine.
Vaccine efficacy reported from trials can vary widely from place to place and time to time. For instance in trials of a Novavax vaccine tested in two places, the efficacy was 89%in the UK and 60%in Africa. (This one is not available in Australia) The difference can be due to varying intensity of the epidemic, and variation in the circulating strains. It has long been known that effectiveness of the annual flu vaccine varies from year to year depending on how good the match is between the vaccine and the circulating strain. The ideal vaccine is one effective against the viruses circulating later in 2021 and 2022, but they cannot be predicted in advance.
Outside of formal randomised trials the effect of immunisation on the risk of disease can be observed during mass immunisation campaigns. On the 2ndMarch 2021 Public Health England announced that the risk of symptomatic Covid in people over 70 years of age vaccinated with 1 dose of the Pfizer vaccine is reduced by 57-61% and after 1 dose of the Oxford AZ vaccine was reduced by 60-73%.
BRGP doctors eligible for the Astra Zeneca vaccination have been immunised.
Update: On 25th March Astra Zeneca released results of another trial, this one in Chile, Peru and the USA, with 32,000 people, of whom 20% were over 65. It showed 76% efficacy from 2 doses given 4 weeks apart. There were no cases of serious disease or hospitalisation for Covid in the 37 people who became infected despite being in the vaccine group, so once again it is 100% effective at preventing hospitalisation. It is frustrating that there has still not been a trial using a 12 week dosing interval.
How likely are the side effects of fever, fatigue or muscle aches?
The Covid vaccines commonly cause symptoms of feeling unwell , having muscle aches or a fever in the days after the injection. These symptoms occur in 60% to 70% of people, much higher rates than we are used to from other vaccines in current use. In this respect they are more like the old “triple antigen” that was in the infant immunisation schedule up until the 1990s. The following figure is the incidence of side effects by the number of days after vaccination from a trial in which the control group were given a meningitis vaccine called ACWY(2). In this figure the Oxford AZ vaccine is given its technical name: ChAdOx1. The side effects peak on day 2, and giving paracetamol makes little difference. At Brunker Rd we are running immunisation clinics on Saturday mornings, so these symptoms are most likely on the Sunday.
How likely are serious side effects?
In the formal trials, with 12,021 given covid vaccine and 11,724 controls given a meningitis vaccine a serious adverse effect occurred in 0.7% vs 0.8% in controls during a median follow up period of 3.4 months. These adverse events record everything bad that happened to these people, including broken arms, cancers, and appendicitis. There was no single adverse event that stood out as being more frequent in those given covid vaccine. Specifically checking conditions including blood clots, there was one pulmonary embolus and one other thrombosis in vaccine recipients and one DVT in a control.
Blood clots such as deep venous thrombosis (DVT) or Pulmonary embolism (PE) occur in the general population at a rate reported as 1.5 per thousand people per year, which equals 29 per million people per week(3). In Europe and the UK 17 million people have been given the Oxford AZ vaccine in the first 10 weeks of 2021, so we would expect 4,930 immunised people to have a DVT or PE in this time. In fact 37 of these blood clots have been reported through vaccine reporting channels, a tiny proportion of the expected background rate.
Cerebral Venous Sinus Thrombosis
Enough evidence has now accumulated that we believe the Astra Zeneca vaccine causes Cerebral Venous Sinus Thrombosis (CVST)which causes symptoms similar to a stroke. As of 7th April there have been 79 cases and 19 deaths after 20 million vaccines given in the UK. The EU has reported 169 cases from 34 million doses. It happens 1 to 2 weeks after the first dose, no cases have occurred after the second dose. It occurs more commonly in younger people. Adding the reported UK and EU cases gives an incidence of 4.59 cases per million doses. If we guess that 70% of doses given so far are first doses, the incidence in first dose recipients is 6.6 per million vaccine recipients. The UK immunisation committee that reviews the adverse event data says there is a slight trend to higher incidence at younger ages, but this does not mean it occurs only in younger people.
The background rate of CVST as measured in Holland some years ago was 13 per million per year. In the UK or Europe where the risk of dying from Covid is much higher than the risk from CVST the choice is easy.
Comparing the risk of CVST with other risks
Australia has stopped local transmission of covid through excellent public health responses, and great disruption to normal life by intermittent lock downs. The country remains at risk of reintroduction and future outbreaks could escape control if public health responses falter, or a more infectious strain evolves. Living in Newcastle we are currently not at risk of covid, so how should we weigh up the benefits and risks of vaccination?
Assuming that the vaccination protects you from covid for 2 years, what are some other risks you face in the next 2 years?
In a 2 year period 77 Australians were struck by lightning and one in 20 died, so that is 4.1 strikes per million people, about the same as the risk of CVST, and 0.19 deaths per million people. (ref AIHW)
Traffic accidents are much more dangerous, with a risk of 94 deaths per million over 2 years.
In a million women taking an oral contraceptive pill there will be 660 pulmonary embolisms over 2 years(4), of which about 490 are due to the pill use.(5)
Our opinion on CVST risk
For people in group 1b, over 70, the benefit of not having to worry about the next covid cluster outweighs the tiny risk of serious adverse events. As at 9/4/2021, younger people - those under 50 yrs of age are no longer recommended to have the Astra Zenica vaccine unless they are at high risk and have considered the issues should consider the above information on risks.
Are there any groups who should not have the vaccine?
Pregnancy: In Australia Covid vaccination is not recommended during pregnancy, although if a pregnant woman were travelling to a high risk destination further advice should be sought.
Prior Anaphylactic reaction to the covid vaccine or one of its components. Further details can be found on the NSW Health website:
Are there any groups who should bring forward immunisation?
The priority groups determined by the government immunisation program include those working in hotel quarantine and in hospitals who would have contact with known covid cases. In addition there is a case for early immunisation of the household contacts of these people.
Other groups who may wish to accelerate immunisation include those about to undergo cancer treatments, or about to travel overseas. The shortest interval between doses approved by the TGA for the Oxford AZ vaccine is 4 weeks however there is indirect evidence that it gives better protection with a longer dosing interval.
https://www.bmj.com/content/372/bmj.n728 commentary on blood clots 16th March.
https://www.nature.com/articles/d41586-021-00836-z news article on US trial results.
1. Voysey M, Clemens SAC, Madhi SA. Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK. Lancet. 2021;397:99–111.
2. Folegatti PM, Ewer KJ, Aley PK. Safety and immunogenicity of the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2: a preliminary report of a phase 1/2, single-blind, randomised controlled trial. Lancet. 2020;396:467–78.
3. McRae S. Pulmonary Embolism. Aust Fam Physician. 2010;39(7):462-6.
4. Alain Weill MD, Fanny Raguideau, Philippe Ricordeau, Pierre-Olivier Blotière,, Jérémie Rudant FA, Mahmoud Zureik. Low dose oestrogen combined oral contraception and risk of
pulmonary embolism, stroke, and myocardial infarction in five
million French women: cohort study. BMJ. 2016;353:i2002.
5. Lidegaard Ø, Nielsen LH, Skovlund CW, Skjeldestad FE, Løkkegaard E. Risk of venous thromboembolism from use of oral
contraceptives containing different progestogens and
oestrogen doses: Danish cohort study, 2001-9. BMJ. 2011;343:d6423.