When a Covid cluster includes people, who are vaccinated against the virus, one inevitably hears rumbles of complaints from people wondering what the vaccination is for.
But when you read the headlines, you usually see the answer: In most cases, those who have been vaccinated and contracted Covid-19 have not died, have not developed serious symptoms, and have not had need to be hospitalized.
For people not vaccinated in their later years, the risk of dying from Covid is high. For the unvaccinated 80-year-olds, around 32% of people who contract Covid will die from it.
For people over 70, it’s around 14%. (For unvaccinated people in their 60s, it drops to around 3%. And for those under 50, it’s less than 1%.)
The good news is that Pfizer and AstraZeneca are both very effective in preventing serious illness and death from Covid-19, even from the more virulent Delta strain.
So how effective are our vaccines?
Preliminary data from the UK shows that after your first dose of Pfizer or AstraZeneca you are 33% less likely than an unvaccinated person to get the Delta variant.
Two weeks after your second dose, this rises to 60% for AstraZeneca and 88% for Pfizer. These data relate to any form of Covid-19, from mild to severe.
But when you look at how well vaccines lower your risk of developing serious illness requiring hospitalization, coverage is high for both.
Pfizer and Astrazeneca vaccines are 96% and 92% (respectively) effective in preventing Delta variant hospitalizations.
Why do some people still contract Covid after being vaccinated?
Vaccines are not magic barriers. They do not kill the virus or the pathogen they are targeting.
Rather, vaccines stimulate a person’s immune system to create antibodies.
These antibodies are specific for the virus or vaccine pathogen and allow the body to fight infection before it sets in and causes serious illness.
However, some people will not have a strong enough immune response to the vaccine and may still be susceptible to developing Covid-19 if exposed to the virus.
How a person responds to a vaccine is influenced by a number of host factors including our age, gender, medications, diet, exercise, health, and stress levels.
It is not easy to tell who has not developed a strong enough immune response to the vaccine. Measuring a person’s immune response to a vaccine is not straightforward and requires detailed laboratory tests.
And while the side effects of the vaccine indicate that you have a response, the absence of symptoms does not mean that you have a weak response.
It also takes time for the immune system to respond to vaccines and produce antibodies.
For most two-shot vaccines, antibody levels rise and then fall after the first dose. These antibodies are then boosted after the second.
But you are not optimally covered until your antibody levels increase after the second dose.
What does the Covid look like after being vaccinated?
The PCR tests we use to detect SARS-CoV-2, the virus that causes Covid-19, are very sensitive and can detect a positive case even if you have low levels of the virus in your system.
This means that a person can test positive for SARS-CoV-2 but still does not have symptoms of Covid-19.
Of those vaccinated who have reported symptoms, the vast majority report mild symptoms, with shorter duration.
There is always a chance that a vaccinated person can pass the virus to an unvaccinated person without having symptoms themselves.
But vaccinated people who develop Covid-19 will likely have a lower viral load than unvaccinated people, meaning they are less likely to spread the virus.
One study estimated that those who were vaccinated with Pfizer or AstraZeneca were 50% less likely to pass it to an unvaccinated family contact than someone who was not vaccinated.
This transmission is likely to decrease again if both household members are vaccinated.
But if you are not vaccinated and contract Covid-19, you are much more likely to spread the virus.
And the future variants?
So far, preliminary data (some of which is ongoing and / or yet to be peer reviewed) shows that our current vaccines are effective in protecting against circulating variants.
But as the virus mutates, the chances of viral leakage increase. This means that there is a greater chance that the virus will develop mutations that make it more apt or more easily able to evade vaccinations.
Scientists are watching closely to ensure that our current and / or future vaccines are effective against circulating strains.
To help fight Covid-19, the best thing we can do is to minimize the spread of the virus.
This means getting the vaccine when you can, making sure you maintain social distancing when necessary, and getting tested if you have symptoms.