Among the nearly one million Israelis vaccinated against the coronavirus so far, about 240 Israelis were diagnosed with the virus within days of receiving the injection, Channel 13 News reported on Thursday.
The figure highlights the need for individuals to continue protecting themselves for weeks after inoculation, as the body takes time to develop effective antibodies against the SARS-CoV-2 virus, which causes COVID-19.
The Pfizer vaccine is not made with the coronavirus itself, which means that there is no chance of anyone getting it from the injections. Instead, the vaccine contains a fragment of genetic code that trains the immune system to recognize the protein fortified on the virus’s surface and create antibodies to attack if it finds the real thing.
Get the daily edition of The Times of Israel by email and never miss our top news.
But that process takes time, and vaccine studies so far have shown that immunity to the virus increases only about 8 to 10 days after the first injection – and then to about 50 percent effectiveness.
That is why the second dose of the vaccine, given 21 days after the first, is critical: it strengthens the immune system’s response to the virus, bringing it to 95% effectiveness and ensuring that immunity lasts. This level of immunity is reached only about a week after the second dose – or 28 days after the first dose.
Anyone who is infected a few days before receiving the first dose of the vaccine or weeks before its full effectiveness is reached is still at risk of developing symptoms (even when the vaccine has reached its maximum potential, there is still a 5% chance).
Man receives COVID-19 vaccine at a Jerusalem vaccination station on December 30, 2020. (Noam Revkin Fenton / Flash90)
Another issue to be noted is that studies have not yet determined whether the vaccine allows a person to carry the disease and spread it without becoming ill: It is possible that, while someone’s body would be largely protected from the virus after vaccination, the layers mucous membranes in the nasal passages, out of the reach of antibodies, could still harbor multiplying virus particles.
Although they do not harm the carrier – since any virus that penetrates the body more deeply would be quickly destroyed by the trained immune system – they could still be expelled through the nose and mouth and infect other people.
The vast majority of Israelis who received the vaccine have reported no problems since vaccination. About one in a thousand people reported having suffered mild side effects, with only a few dozen seeking medical attention after the shot, figures released on Wednesday showed.
The most common side effects reported were weakness, dizziness and fever, with 319 cases combined, the ministry said. Five also reported diarrhea. Another 293 people reported localized symptoms where the injection was given, such as pain, restricted movement, swelling and redness.
Fourteen people said they had allergic reactions, such as itching and swelling of the tongue and throat.
In addition, 26 people suffered what the ministry described as “neurological symptoms”, with 19 complaining of a tingling sensation in the arm.
The ministry noted that only 51 people (0.008%) of those who reported having experienced any side effects said they sought medical attention for their symptoms.
According to public broadcaster Kan, there were four cases in which people in Israel died shortly after receiving the vaccination, but three of the four were considered by the Ministry of Health, as well as family members and doctors, to be unrelated to the shots. The fourth case, an 88-year-old man who had serious pre-existing health problems, is being investigated.