The COVID pandemic has been going on for well over two years now. During this time, SARS-CoV-2 (the virus that causes COVID-19) has slowly mutated, allowing it to evade the immune system enough to infect people many times. 

As so many of us have had COVID already, it’s no surprise that plenty of people are catching the virus for a second or even a third time. In the UK, this has been particularly noticeable since the emergence of the omicron variant from December 2021 onwards. 

But when reinfected, are you likely to feel better or worse than you did the first time you had COVID? As well as being a question many people are curious about, this is an important issue from a public health perspective

If symptoms are more severe, each time someone gets infected, we would expect the pandemic to escalate as people become sicker and sicker. A zero-COVID strategy would be the only way to avert waves of serious illness

The alternative is almost precisely the opposite. If each subsequent infection is less severe, the pandemic would eventually fizzle out on its own without the need for masking, quarantine, lockdowns or other measures. 

                                     So what does the evidence say? 

A recent preprint (an article published online before undergoing peer review) was interpreted as suggesting that symptoms of reinfections with COVID are worse than those of initial infections. 

But the authors didn’t specifically look at symptom severity. They looked at the likelihood of death from any cause, hospitalisation, and a variety of health problems within six months after infection. The researchers concluded that these measures were worse after reinfections.

While this isn’t good news, the results need to be interpreted carefully. The data used in this study comes from electronic healthcare records of over 5 million US army veterans, over 290,000 of whom had COVID at least once. 

For a start, the group studied was already at higher risk of experiencing worse outcomes compared with the overall population. The average age was 60, around 20% smoked and more than 80% of those who contracted COVID were not vaccinated. So the results may not apply to the general population.

Second, the reinfection group were analysed immediately after reinfection, while the initial infection group were not analysed until 30 days following infection. This means that the outcomes observed for reinfection include all the early COVID symptoms (headache, cough, fatigue and so on) which the other group may have recovered from. As the data included any symptoms or health problems that occurred within the study period, including acute infection in one group skews the findings, making reinfections appear worse.