A firsthand experience

CLINICAL MATTERS

Got the booster! My primary vaccine series was Sinovac, and I was given a Pfizer booster. I was the second person to get vaccinated with Sinovac in the Philippines, right after PGH director Gerardo Legaspi. Since I got my first dose last March 1, 2021 and my second dose weeks later, I was among the first to qualify for a booster when the FDA announced that they were amending the Emergency Use Authorizations (EUAs) of the different vaccines to allow a third vaccine dose initially for the A1 priority group. Since then, A2 seniors and immunocompromised A3 have also started receiving their shots.

With the US CDC now recommending booster shots to anyone above 18 years old, it may be just a matter of time and availability before every person is offered a booster. The column this week outlines my decision process and the side effects I felt after my shot. With hope, this will help people make up their minds on a booster if and when it is offered.

As a huge proponent of getting as many people vaccinated as soon as possible, I was torn on whether or not I would accept the booster being offered by the government to frontline workers. With only about 40 percent of the target population in the Philippines fully vaccinated, it did not feel right that I would be taking an extra dose while there were still many people who had not been given a chance at basic protection. Given the scientific uncertainties of the benefits of boosters versus the known benefits of primary vaccination, it did not seem fair to get marginally added protection from something that could very well save someone else’s life.

Dr. John Wong, the resident epidemiologist of the Technical Advisory Group of the Department of Health, has calculated that the number of hospitalizations prevented by prioritizing primary vaccination is five times more than hospitalizations prevented by boosters. People who already have the vaccine retain protection against severe disease, and the added protection with boosters is much smaller than the protection from COVID-19 that primary series vaccination gives to an unvaccinated person.

There were two things that finally convinced me to take the booster. The first was that vaccine czar Secretary Carlito Galvez assured us that there was enough supply for healthcare workers’ booster doses. He also pointed out that healthcare workers’ morale was very important for the nation and that he personally felt that healthcare workers deserved any added protection the government could provide.

The second thing that changed my mind was new data from the Centers for Disease Control that they used to further recommend boosters to adults 18 years old and above. Previous data in support of booster use mostly showed increases in antibody levels and not necessarily prevention of clinical disease. The newest data now shows modest but real increase in clinical effectiveness across all age and patient groups. While the efficacy against severe disease remains high, this new data clearly shows that there is some benefit to boosters after six months. For frontline healthcare workers who are highly exposed to COVID-19 patients, every additional percentage increase in protection can mean the difference between being able to continue taking care of patients versus taking time off to nurse a clinical infection. It also decreases the risk of passing on a COVID-19 infection to other patients.

The next decision was which booster to take. Having taken Sinovac, I had four choices: a third dose of Sinovac, Pfizer, Moderna at half dose, or Astra. Most data only showed antibody levels going up after boosting, but there was limited real-world clinical data. There wasn’t much comparing these choices head-to-head, but there was a relevant study done in Chile involving over two million people with some preliminary results. In the study, boosters were offered to subjects who had gotten two doses of Sinovac as a primary series. The study investigators divided the subjects into three groups: One group got a third dose of Sinovac, another group got a Pfizer booster, and the third group got an Astra booster. The initial results showed that that all three boosters protected well against severe disease with minimal differences. All three increased the clinical protection from a baseline of 56 percent to 80 percent, 90 percent, and 93 percent respectively. All three increased efficacy against severe disease from 84 percent to 88 percent, 87 percent, and 96 percent respectively. It was unclear whether these differences were statistically significant without more data, but the huge numbers from this study were compelling.

The final consideration was the risk of side effects. There is data that shows heterologous vaccination, i.e., mixing one vaccine type with another, is associated with a higher risk of reactions. This is particularly true with boosting with mRNA vaccines as they are the most immunogenic. Given my status as a healthcare worker who is relatively healthy with no history of allergies, I considered that I could risk a worse reaction with an mRNA booster or Astra for the modest added protection over a Sinovac. This is not a strategy I would recommend for frail elderly people, or those who have allergies.

As I was mulling my options, the text message came from the Philippine General Hospital vaccination center. I was invited to get a Pfizer booster in two days. I could either go ahead and take it, or wait for either Astra or a third dose of Sinovac when it became available. Going by the principle that I used to decide when I first got my primary series, i.e., the best vaccine is the one in your arm, I opted to proceed and I texted “yes.”

The day came and I went to the outpatient department of the Philippine General Hospital. There was a bunch of people in line when I arrived. The process was relatively efficient, consisting of verification of personal data, vitals, and finally the shot. The Pfizer shot was a bit more painful than I remembered the two Sinovac shots had been. My arm felt heavy but it was bearable. I was monitored for 15 minutes and released. I went back to the clinic then started to do my hospital rounds. The arm was starting to feel heavier, and a mild numbness was evident.

When I arrived home that afternoon, it was starting to hurt. I took a shower and walked around the neighborhood and felt better, but it was still pretty heavy. I went to sleep with little trouble. The next day, the arm was hurting a bit more but was less numb. I did rounds in the hospital and went home. Then I started to feel joint pains. Everything felt inflamed. I gave in, took a dose of paracetamol and turned in early. The next day, I felt human again and the pain gradually improved over the next couple of days.

Overall, it was not a pleasant experience but I’m glad I did it. Would I have preferred to take a homologous dose? Probably not since I work as a healthcare worker on the front line. If I did not have this degree of exposure, it would be very tempting to get a third dose of Sinovac. When the time comes for you to decide on a booster, the things to think about are your risk of getting COVID-19 and your risk of significant side effects. Are you willing to risk bad side effects for a modest increase in efficacy? The answer to this question is unique to each person. Not taking a booster remains an option while waiting for more data. Protection against severe disease remains robust beyond six months. If you’re still stuck, talk to your doctor for guidance. Remember that being able to get a booster remains a huge privilege, as many people worldwide are still unable to get a primary vaccine course. In the end, the added protection is a bonus, and being able to get one should never be taken for granted.