Since 2020, the biggest problem the world faces has remained the Covid-19 pandemic. Over time, it has both caused disease and death as well as crippled economies and normal life. It has become increasingly clear that neither harsh steps like nationwide lockdowns nor more maverick experiments with “herd immunity” are going to succeed at digging humanity out of its present predicament. This has all but left us with the option of vaccinating our way out of this. In this context, the challenge of vaccinating seven and a half billion people has become further compounded by concerns around vaccine safety. In particular, popular discourse around side effects of and, more importantly, adverse reactions to Covid-19 vaccines has very significantly accentuated “vaccine hesitancy”. This has led to (previously avoidable) slowdowns in vaccine roll-outs and setbacks to national vaccination efforts. Let us try to take a step forward in this direction – by trying to understand the issue of adverse reactions to Covid-19 vaccines. To do this, we will use broad examples. In particular, let us take up Quetta and assume that it has a population of precisely 01 million. Next, for our purposes, let us take up the AstraZeneca-Oxford University Covid-19 vaccine, the most misunderstood and, therefore, controversial of all vaccines currently available. Now, the problem with Covid vaccines is that people report side-effects after getting the vaccine, such as feeling pain in their arm, temporary Covid-like symptoms, headache, tiredness, etc. The side-effects are a relatively smaller issue. They are a fairly common occurrence and are, simply, a result of the medicine people are getting. All these symptoms are temporary and pass quickly (i.e. within 12 to 48 hrs). In this context, it is important to note that all medicines have some sort of a side-effect. Even the commonly used Panadol or an easily available antibiotic have their own side-effects. For example, both can cause upset stomachs, loss of appetite, indigestion or even vomiting. Thus, vaccines also causing some side-effects should not serve as cause for alarm. However, like everything else – say, milk – vaccines are also chemical compounds. Like everything else – again, say, milk which is a problem for the lactose intolerant – chemicals that make up a vaccine can trigger some sort of allergic reaction. Or, these chemicals can have some sort of adverse effect on a human body unto itself. For instance, chemotherapy that treats cancer causes hair fall. Similarly, it is quite possible that the chemicals that make up a vaccine can cause a negative reaction in the human body. These are called “adverse reactions to a vaccine” or ADRs. In case of some Covid vaccines, especially AstraZeneca (but also, Janssen and Sputnik!), there have been reports that an “adverse reaction” (or, ADR) takes the form of platelets in some people’s blood sticking together and forming big lumps. This process is called “thrombosis” and the lumps are called “blood clots”. In some – again, some – extreme – again, extreme – cases, the process of platelets sticking together accelerates to an extent that huge numbers of platelets stick together, leading to a significant drop in platelet counts in blood. This is a condition called thrombocytopenia. This relatively unique situation where conditions of thrombosis and thrombocytopenia both take hold, has become the greatest cause of concern around vaccines like AstraZeneca. So then, how can we navigate an understanding around ADRs? Broadly, we can do three things: 1) We can try to see how common ADRs, especially the “blood clotting”, phenomenon is to judge its impact on us and people around us; 2) We can try to see what happened in other places where vaccines like AstraZeneca were administered; and, 3) We can do a cost-benefit analysis and weigh cost of accepting risks of ADRs like “blood clots” against benefits of administering vaccines like AstraZeneca to people. On the first count, our job has been made easy by research undertaken by respected public health organizations such as World Health Organization (WHO) and European Medical Agency (EMA). Such organizations have calculated that the chance of developing ADRs like thrombosis with thrombocytopenia (henceforward, simply “blood clots”), is about 0.001% after one dose of, for example, AstraZeneca and 0.0001% after its two doses. This means that 01 person in every 100,000 people given AstraZeneca will develop a blood clot after one dose and 01 in every 1 million will develop a clot after two doses. Adapting these figures to Quetta’s example, we can see that if all 01 million Quetta residents are given AstraZeneca, we should expect to find 10 people who develop a blood clot. Further, research has shown that only 20% of the people who do develop clots might die of it. This should mean that of the 10 cases of blood clotting, only two (02) persons may die. So now, what is the trade-off? The current global average “case fatality ratio” of Covid-19 disease comes to about 2.08%. Or, 2.08% of all people who get Covid tend to pass away. If we use this ratio for our Quetta example, we can see that if all 01 million Quetta citizens get Covid, we can expect 20,800 people to die. This is the worst-case scenario and is just an illustrative example. In any case, the choice before us comes to this: Do we want to accept the risk of two of Quetta’s citizens possibly dying and save all the remainder, or, do we want to reject AstraZeneca, allow Quetta’s population to contract Covid and, then, accept the loss of 20,800 lives. International organizations and hundreds of governments around the world, have already done this type of math. They have seen that, to quote words from the most common verdict on AstraZeneca vaccine, ‘the benefits of administering vaccines, including AstraZeneca, far outweigh the risks of the same’. In other words, where the choice is between 20,800 dead vs. just two possible deaths, international organizations as well as world governments have chosen to accept the risk of the latter happening. This determination has led to repeated emphasis by the WHO to continue administration of vaccines, including AstraZeneca, on the one hand. On the other, it has led to the EMA designating blood clots a “very rare side effect”. This is because this designation reflects the fact. That is to say, blood clots are, indeed, an extremely rare side-effect. At 0.001%, the probability of getting a clot is extremely low. It is so low that it is exactly equal to you dying after getting hit by lighting. It is so low, in fact, that it is half of the chance that you will die after getting hit by a car while walking along a road today! Within this context, hundreds of countries are continuing to administer vaccines, especially AstraZeneca. For instance, about 70% of the 210 million doses administered in India have been AstraZeneca. How many blood clot cases have been found amongst 147 million doses? Around 50! Over 21 million doses of AstraZeneca have been administered in Latin America. How many of these have resulted in deaths so far? Zero! In the UK, over 68 million Covid vaccine doses have been administered of which about a third are AstraZeneca. The government of UK conducted a specific study on the clotting matter that was released on May 12. In this report, UK noted that it had only logged 309 suspected cases of blood clots from amongst 32 million doses that had by then been administered. This comes to just 0.00096% of the sample. Interestingly, the same report notes that this percentage is actually below the average estimated number of people who would get blood clots anyway due to other reasons during the same period of study! These are just a few examples. There is plenty of data out there that demonstrates that vaccines, including AstraZeneca, work and that adverse events are extremely rare. One need not go any farther than this: Infectivity in the UK, AstraZeneca’s second biggest user, has dropped to just 0.47% today. The pandemic is also coming down in virtually all countries that have been administering vaccines, including AstraZeneca. The results, the data, the science on this matter is clear: Vaccines work. So, should you get a vaccine shot, even if it’s AstraZeneca? The answer to that is a very definite yes. Approved vaccines, including AstraZeneca, cut risk of hospitalization and death by 100%. They cut risk of symptomatic disease by close to 90% – yes, this includes AstraZeneca. So, save yourself some trouble. Rise above the social media brouhaha that is fuelled by limited understanding of science and data as well as a more general suspicion on science, medicine and vaccines. You and your loved ones are stuck in a dire situation. But the path out of it is absolutely sure and clear: Vaccines. Get the shot!